SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
1240 PM PST WED MAR 5 2008
.SHORT TERM...
SATELLITE IMAGERY SHOWING A RAPID BURNOFF OF LOW CLOUDS AND FOG
THIS MORNING AS OFFSHORE FLOW BEGINS TO DEVELOP ACROSS THE REGION.
PRESSURE GRADIENTS WERE ONSHORE LAST NIGHT...BRINGING THE MARINE
LAYER CLOUDS LOCALLY INTO THE VALLEYS...BUT HAVE REVERSED QUICKLY
THIS MORNING. THE PRESSURE GRADIENTS ARE EXPECTED TO TREND OFFSHORE
DURING THE NEXT FEW HOURS...WITH SOME INCREASING OFFSHORE WINDS
BEING DEPCITED AT THE 850 MB LEVEL. ALREADY SEEING SOME WINDS GUSTING
BETWEEN 30 AND 40 MPH THIS MORNING ACROSS THE LA COUNTY MOUNTAINS.
WITH GRADUAL INCREASE IN OFFSHORE PRESSURE GRADIENT AND UPPER LEVEL
SUPPORT DURING THE NEXT FEW HOURS...SHOULD SEE SOME ADDITIONAL
INCREASE IN AREAL COVERAGE AND INTENSITY OF OFFSHORE WINDS. AT THIS
POINT...GENERALLY EXPECTING WINDS TO REMAIN JUST BELOW ADVISORY
CRITERIA...WITH SOME OF THE FAVORED MOUNTAIN PASSES GUSTING TO 45
MPH TODAY...WHILE SOME FAVORED VALLEY LOCATIONS COULD PEAK AROUND 35
MPH. AT THIS TIME...THE OFFSHORE WINDS HAVE NOT REALLY SURFACED INTO
THE VALLEYS AS LATEST ACARS DATA SHOWING WINDS REMAINING ABOVE
MARINE INVERSION...CURRENTLY LOCATED AROUND 1700 FEET.
HOWEVER...WITH SOME DAYTIME HEATING...WOULD EXPECT THE OFFSHORE
WINDS TO SURFACE IN SOME OF THE FAVORED VALLEY LOCATIONS DURING THE
NEXT HOUR OR TWO. IN MORNING UPDATE...HAVE INCLUDED MENTION OF SOME
OFFSHORE WINDS IN THE VALLEYS...ALONG WITH BUMPING UP TEMPERATURES A
FEW DEGREES IN SEVERAL ZONES.
THE OFFSHORE WINDS ARE EXPECTED TO REINTENSIFY OVERNIGHT INTO
THURSDAY MORNING...BUT ARE GENERALLY EXPECTED TO REMAIN JUST BELOW
ADVISORY LEVELS. THE OFFSHORE TRENDS ARE EXPECTED TO KEEP SKIES
MOSTLY CLEAR TONIGHT...FOLLOWED BY ANOTHER FAIRLY WARM DAY ON
THURSDAY.
*** FROM PREVIOUS DISCUSSION ***
A WEAK RIDGE NOSES INTO THE AREA FRIDAY. THIS IS THE WEATHER FEATURE
THERE IS ALSO A WEAK UPPER LEVEL LOW MOVING TO THE WEST AND SOUTH OF
THE AREA BUT THIS WILL DO LITTLE IF ANYTHING. THE HGTS AND SFC GRADS
ARE SIMILAR AND EXPECT MAX TEMPS TO LOOK SIMILAR TO THURSDAY.
.LONG TERM...
GFS AND EC NOT IN THE BEST AGREEMENT...BUT NOT AS BAD AS LAST NIGHTS
RAIN OR NO RAIN SCENARIO. BOTH MDLS ARE DRY. DIFFERENCE LAY IN THE
TIMING AND LOCATIONS OF MANY LITTLE RIPPLES IN THE FLOW TO THE NORTH
AND THE EAST OF US. THE BIG CHANGE IN THE FORECAST WILL BE THE
RETURN OF ONSHORE FLOW SAT NIGHT AND SUN NIGHT WHICH SHOULD AT LEAST
GIN UP A MARINE LAYER FOR L.A. COUNTY AND COULD POSSIBLY REACH THE
LOWER L.A. VLY AS WELL AS THE VTA COAST. HIGH LEVEL CLOUDS WILL KEEP
THINGS PARTLY CLOUDY WHERE THERE ARE NOT MARINE CLOUDS. TEMPS WILL
FALL.
&&
.AVIATION...05/2030Z
CLEAR SKIES AND UNRESTRICTED VISIBILITIES ARE EXPECTED THROUGH
THURSDAY. SOME WIND PRONE AREAS CAN EXPECT GUSTY WINDS...TURBULENCE
AND LOW LEVEL WIND SHEAR. SUCH LOCATIONS INCLUDE KOXR (AS EVIDENCED
BY RECENT PILOT REPORTS)...KBUR...KVNY...KPMD AND KWJF. OTHER
LOCATIONS WILL HAVE SOME WIND POTENTIAL.
KLAX...HIGH CONFIDENCE IN CLEAR SKIES AND UNRESTRICTED VISIBILITY
THROUGH THURSDAY.
KBUR...HIGH CONFIDENCE IN CLEAR SKIES AND UNRESTRICTED VISIBILITY
THROUGH THURSDAY. LOCALLY GUSTY WINDS AND LOW LEVEL WIND SHEAR
POSSIBLE.
$$
.LOX WATCHES/WARNINGS/ADVISORIES...
NONE
&&
$$
PUBLIC...GOMBERG/RORKE
AVIATION...SWEET
WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
930 AM PST WED MAR 5 2008
.SYNOPSIS...
GENERALLY NORTHWEST FLOW PATTERN WILL BRING DRY...MOSTLY FAIR
WEATHER THROUGH EARLY NEXT WEEK WITH PATCHY LOW CLOUDS NEAR THE
COAST AT TIMES AND BRIEF PERIODS OF GUSTY OFFSHORE WINDS FOR INLAND
AREAS.
&&
.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
.SHORT TERM...TODAY THROUGH FRIDAY...
MODELS IN AGREEMENT TAKING WEAK UPPER LOW CURRENTLY OFF THE
SOUTHWEST CALIFORNIA/NORTHERN BAJA CALIFORNIA COAST SOUTHEAST TODAY
AS HIGH PRESSURE RIDGE BUILDS ALONG 125W LONGITUDE. RIDGE TO SHIFT
INLAND TO 120W TONIGHT/THURSDAY AS A TROUGH BUMPS INTO THE RIDGE.
THURSDAY NIGHT/FRIDAY THIS TROUGH ALSO EXPECTED TO SLIDE SOUTHEAST
DEVELOPING ANOTHER WEAK UPPER LOW PRETTY MUCH IN THE SAME PLACE THE
CURRENT ONE IS. FOR TODAY ANOTHER SANTA ANA WIND EVENT SHAPING UP
WITH THE HIGH PRESSURE RIDGE BUILDING AND OFFSHORE PRESSURE
GRADEINTS 15 MB BETWEEN NE NEVADA AND INLAND EMPIRE THIS MORNING AND
REMAINING 10 TO 13 MB TONIGHT THROUGH THURSDAY MORNING. LOCAL WIND
PROGRAM USING NGM...NAM...AND GFS...INDICATES GUSTS 60 TO 81 MPH
BELOW CAJON PASS AND IN SANTA ANA MOUNTAINS THIS MORNING...THEN
FALLING OFF TO AROUND 50 MPH THIS AFTERNOON THROUGH THURSDAY
MORNING. HOWEVER WINDS ALOFT BOTH OBSERVED AND PREDICTED DO NOT
SUPPORT THESE HIGHER NUMBERS AND THE STRONGER PRESSURE GRADEINTS ARE
MORE NORTH TO SOUTH DOWN THE COLORADO RIVER BASIN. ALSO THE
LINGERING COASTAL EDDY AND DEEPER MARINE LAYER IS RETARDING THE
ONSET. CONSIDERING THE SHORT DURATION ON THE WINDS WILL HOLD WITH
CURRENT WIND ADVISORY BUT BEEF UP WORDING TO INDICATE GUSTS OVER 50
MPH AND CONSIDER EXTENDING THE ADVISORY BEYOND 2 PM AS WINDS ALOFT
INCREASE TO SUPPORT GUSTS AROUND 45 MPH. NO OTHER CHANGE
CONTEMPLATED AT THIS TIME.
&&
.LONG TERM FROM PREVIOUS DISCUSSION...SATURDAY THROUGH TUESDAY...
HIGH PRESSURE ALOFT WILL CONTINUE FAIR...DRY WEATHER THROUGH MONDAY
WITH A RETURN OF THE MARINE LAYER POSSIBLE FOR SUNDAY AND MONDAY.
FOR TUESDAY THROUGH MIDWEEK...MODELS ARE TRENDING FARTHER NORTH WITH
A SHORTWAVE MOVING INLAND ALONG THE WEST COAST. WHILE THIS WOULD
STILL BRING COOLING AND SOME INCREASE IN CLOUDS...THE MORE NORTHERN
TRACK WOULD KEEP PRECIPITATION TO THE NORTH OF SOUTHWEST CALIFORNIA.
&&
.AVIATION...
051530Z...MARINE LAYER DEPTH WAS AROUND 2000 FEET THIS MORNING BASED
ON MDCRS SOUNDINGS AND MORNING TOP REPORTS. EXPECT THE MARINE LAYER
DEPTH TO LOWER TODAY AS OFFSHORE FLOW DEVELOPS OVER THE AREA. COAST
EDDY WHICH IS HELPING TO MAINTAIN THE MARINE LAYER SHOULD DISSPATE
THIS MORNING AS THE OFFSHORE FLOW DEVELOPS.
STRATUS ALONG THE COAST AND OVER THE INLAND VALLEY AREAS WITH BASES
BETWEEN 1500 AND 2000 FEET MSL SHOULD SCATTER OUT BETWEEN 16Z AND
18Z THIS MORNING. OTHERWISE SCATTERED TO BROKEN CLOUDS AT OR ABOVE
FL200 WITH UNRESTRICTED VISIBILITIES WILL DOMINATE THROUGH THURSDAY.
LOCAL GUSTY NORTHEAST WINDS THROUGH AND BELOW MOUNTAIN PASSES AND
CANYONS WITH ASSOCIATED UP AND DOWN DRAFTS AND LOW LEVEL WIND SHEAR
THROUGH THURSDAY MORNING...ESPECIALLY VICINITY KONT. HORTON
&&
.SGX WATCHES/WARNINGS/ADVISORIES...
CA...WIND ADVISORY FROM 8 AM THIS MORNING TO 2 PM PST THIS AFTERNOON
FOR SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND
EMPIRE-SANTA ANA MOUNTAINS AND FOOTHILLS.
PZ...NONE.
&&
$$
PUBLIC/FIRE WEATHER...BALFOUR
AVIATION/MARINE...HORTON
NWS ON THE WEB AT WEATHER.GOV/SANDIEGO
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
915 AM PST WED MAR 5 2008
.SHORT TERM...
SATELLITE IMAGERY SHOWING A RAPID BURNOFF OF LOW CLOUDS AND FOG
THIS MORNING AS OFFSHORE FLOW BEGINS TO DEVELOP ACROSS THE REGION.
PRESSURE GRADIENTS WERE ONSHORE LAST NIGHT...BRINGING THE MARINE
LAYER CLOUDS LOCALLY INTO THE VALLEYS...BUT HAVE REVERSED QUICKLY
THIS MORNING. THE PRESSURE GRADIENTS ARE EXPECTED TO TREND OFFSHORE
DURING THE NEXT FEW HOURS...WITH SOME INCREASING OFFSHORE WINDS
BEING DEPCITED AT THE 850 MB LEVEL. ALREADY SEEING SOME WINDS GUSTING
BETWEEN 30 AND 40 MPH THIS MORNING ACROSS THE LA COUNTY MOUNTAINS.
WITH GRADUAL INCREASE IN OFFSHORE PRESSURE GRADIENT AND UPPER LEVEL
SUPPORT DURING THE NEXT FEW HOURS...SHOULD SEE SOME ADDITIONAL INCREASE
IN AREAL COVERAGE AND INTENSITY OF OFFSHORE WINDS. AT THIS POINT...
GENERALLY EXPECTING WINDS TO REMAIN JUST BELOW ADVISORY CRITERIA...WITH
SOME OF THE FAVORED MOUNTAIN PASSES GUSTING TO 45 MPH TODAY...WHILE
SOME FAVORED VALLEY LOCATIONS COULD PEAK AROUND 35 MPH. AT THIS
TIME...THE OFFSHORE WINDS HAVE NOT REALLY SURFACED INTO THE VALLEYS
AS LATEST ACARS DATA SHOWING WINDS REMAINING ABOVE MARINE INVERSION...
CURRENTLY LOCATED AROUND 1700 FEET. HOWEVER...WITH SOME DAYTIME
HEATING...WOULD EXPECT THE OFFSHORE WINDS TO SURFACE IN SOME OF THE
FAVORED VALLEY LOCATIONS DURING THE NEXT HOUR OR TWO. IN MORNING
UPDATE...HAVE INCLUDED MENTION OF SOME OFFSHORE WINDS IN THE
VALLEYS...ALONG WITH BUMPING UP TEMPERATURES A FEW DEGREES IN
SEVERAL ZONES.
THE OFFSHORE WINDS ARE EXPECTED TO REINTENSIFY OVERNIGHT INTO
THURSDAY MORNING...BUT ARE GENERALLY EXPECTED TO REMAIN JUST BELOW
ADVISORY LEVELS. THE OFFSHORE TRENDS ARE EXPECTED TO KEEP SKIES
MOSTLY CLEAR TONIGHT...FOLLOWED BY ANOTHER FAIRLY WARM DAY ON THURSDAY.
*** FROM PREVIOUS DISCUSSION ***
A WEAK RIDGE NOSES INTO THE AREA FRIDAY. THIS IS THE WEATHER FEATURE
THERE IS ALSO A WEAK UPPER LEVEL LOW MOVING TO THE WEST AND SOUTH OF
THE AREA BUT THIS WILL DO LITTLE IF ANYTHING. THE HGTS AND SFC GRADS
ARE SIMILAR AND EXPECT MAX TEMPS TO LOOK SIMILAR TO THURSDAY.
.LONG TERM...
GFS AND EC NOT IN THE BEST AGREEMENT...BUT NOT AS BAD AS LAST NIGHTS
RAIN OR NO RAIN SCENARIO. BOTH MDLS ARE DRY. DIFFERENCE LAY IN THE
TIMING AND LOCATIONS OF MANY LITTLE RIPPLES IN THE FLOW TO THE NORTH
AND THE EAST OF US. THE BIG CHANGE IN THE FORECAST WILL BE THE
RETURN OF ONSHORE FLOW SAT NIGHT AND SUN NIGHT WHICH SHOULD AT LEAST
GIN UP A MARINE LAYER FOR L.A. COUNTY AND COULD POSSIBLY REACH THE
LOWER L.A. VLY AS WELL AS THE VTA COAST. HIGH LEVEL CLOUDS WILL KEEP
THINGS PARTLY CLOUDY WHERE THERE ARE NOT MARINE CLOUDS. TEMPS WILL
FALL.
&&
.AVIATION...05/1130Z
MARINE LAYER MAKING A VERY ANNOYING TAG TEAM WITH HIGH CLOUD
DRIFTING OVERHEAD. MARINE LAYER DECK IS NOT SOLID...SO THE HIGH
CLOUDS CONTINUE TO MAKE FOR A LOW CONFIDENCE STRATUS FORECAST THIS
MORNING FOR COASTAL AND VALLEY TAFS. THIS PROBLEM SHOULD END AROUND
18Z AS SOME OFFSHORE FLOW DEVELOPS ACROSS THE AREA. VFR CONDS WITH
SOME LOCAL NORTH TO NORTHEAST WINDS CAN BE EXPECTED TONIGHT.
KLAX...LOW CONFIDENCE FORECAST THIS MORNING WITH REGARD TO BKN-OVC
MVFR DECK. WILL FORECAST BKN CONDS THRU ABOUT 17Z...THEN CLEAR
AIRFIELD OUT. HIGH CONFIDENCE IN VFR CONDS FROM THIS AFTERNOON
THROUGH 12Z THURSDAY. SOME LIGHT 5-7 KNOT EASTERLY WINDS CAN BE
EXPECTED THIS MORNING...AND AGAIN AFTER 10Z TONIGHT. OTHERWISE...
TYPICAL 8-10 KNOT SEA BREEZE THIS AFTERNOON.
KBUR...HIGH CLOUDS MAKE FOR DIFFICULTY OBSERVING LOW CLOUDS REPORTED
AT THE AIRFIELD. OVERALL...LOW CONFIDENCE WITH REGARD TO IFR CLOUD
DECK THIS MORNING. WILL FORECAST BKN-OVC IFR CONDS THROUGH ABOUT
15Z...THEN WILL EXPECT CLEARING CONDITIONS. LOW CLOUD PROBLEM SHOULD
END LATER THIS MORNING AS OFFSHORE FLOW BEGINS TO DEVELOP. HIGH
CONFIDENCE FORECAST IN FVR CONDS FROM THIS AFTERNOON THROUGH 12Z
THURSDAY. WEAK AFTERNOON SE SEABREEZE WILL DEVELOP...WITH SOME WEAK
NORTHERLY WINDS EXPECTED THIS EVENING. THE OFFSHORE FLOW...IF STRONG
ENOUGH...COULD PRODUCE SOME WIND SHEAR PROBLEMS THIS EVENING AND
OVERNIGHT.
$$
.LOX WATCHES/WARNINGS/ADVISORIES...
NONE
&&
$$
PUBLIC...GOMBERG/RORKE
AVIATION...THOMPSON
WWW.WEATHER.GOV/LOSANGELES
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
751 PM CST WED MAR 5 2008
.DISCUSSION...
750 PM CST
UPDATED GRIDS/TEXT PRODUCTS TO BACK OFF A BIT ON SNOW ACROSS MUCH
OF THE CWA. DRY LEVELS ARE REALLY DO QUITE A NUMBER OF EATING AWAY
AT THE SNOW WITH RECENT TRENDS IN KLOT-88D INDICATING PRECIP IS
ONLY MAKING IT AS LOW AS ABOUT 4500FT AGL BEFORE
EVAPORATING...WITH NO APPRECIABLE TREND OF THIS PRECIPITATION
GETTING CLOSER TO THE SURFACE OVER THE PAST SEVERAL HOURS.
UPSTREAM...APPEARS AS THOUGH DEPTH OF THE CLOUDINESS IS DECREASING
PER DVN VWP.
TOWARD THE WI LINE COULD STILL SOME SOME LIGHT SNOW/FLURRIES WITH
MAYBE JUST A SMIDGE OVER A DUSTING POSSIBLE. ELSEWHERE WOULD
EXPECT NO ACCUMULATION AND JUST FLURRIES OR A BRIEF SNOW SHOWER AT
BEST (OR WORST AS THE CASE MAY BE).
UPDATED GRIDS/DERIVED PRODUCTS REFLECTING THE LATEST THINKING HAVE
ALREADY BEEN SHIPPED.
IZZI
&&
.PREV DISCUSSION...
302 PM CST
INITIAL FOCUS IS ON THE SNOW CHANCES FOR THIS AFTERNOON INTO THE
NIGHT AS A WEAK CLIPPER SYSTEM CONTINUES ITS PROGRESS INTO
NORTHERN ILLINOIS. SFC LOW CURRENTLY ANALYZED IN SE IOWA WILL
PROPAGATE EASTWARD INTO NORTHERN ILLINOIS TONIGHT AND THEN ON INTO
MICHIGAN BY THURSDAY MORNING. CONCEPTUALLY...THE GFS SEEMS TO HAVE
A BETTER HANDLE ON THE SNOW/PRECIP WITH THIS SYSTEM...WITH THE
BULK OF THE SNOW FALLING JUST TO THE NORTH OF THE TRACK OF THE LOW
AND THE WARM FRONT EXTENDING EAST OUT OF THE LOW. LOOKS LIKE THERE
COULD ALSO BE A QUICK SHOT FOR SOME LIGHT SNOW ALONG AND AHEAD OF
THE COLD FRONT SOUTH OF THE LOW. VISIBILITIES OUT IN EASTERN IOWA
HAVE BEEN AS LOW AS 1/2SM AT TIMES...BUT FOR THE MOST PART HAVE
BEEN IN THE 1 TO 5 MILE RANGE. WITH NOT A LOT OF MOISTURE TO WORK
WITH...LIKELY WONT SEE MUCH ACCUMULATION OUT OF THIS WITH A
DUSTING TO A HALF INCH MOST LIKELY. HIGHER AMOUNTS WILL LIKELY
STAY NORTH OF THE GREAT WEATHER DIVIDER IN NORTHERN ILLINOIS KNOWN
AS I-80. ALL THIS SAID...CONFIDENCE IS LOW IN HOW MUCH SNOW WILL
FALL DUE TO THE WEAK NATURE OF THIS SFC LOW AND THERE REALLY BEING
NO STRONG FOCUS WITH THE LOW...BUT IT DOES LOOK LIKE WE WILL AT
LEAST SEE SOME FLAKES.
AFTER THIS SYSTEM MOVES OUT OF THE REGION...A REINFORCING SHOT OF
COLD AIR WILL DROP DOWN ON THURSDAY NIGHT. ALONG THE LEADING EDGE
OF THE COLD AIR...SOME SCATTERED FLURRIES WILL BE POSSIBLE. THE
GFS IS TRYING TO PUMP OUT SOME MEASURABLE PRECIP...BUT CURRENT
THINKING IS THAT IT IS OVERDOING IT A BIT. THIS COLD AIR WILL SET
THE STAGE FOR THE NEXT CHANCES FOR SNOW ACROSS NE IL/NW IN.
SETUP SEEMS FAVORABLE FOR LAKE EFFECT SNOW STARTING FRIDAY NIGHT
AS A LOW PRESSURE SYSTEM RAMPS UP IN THE SOUTHERN US AND A 1038MB
HIGH PUSHES DOWN ACROSS THE UPPER MISSISSIPPI RIVER VALLEY REGION.
850MB TEMPS WILL CONTINUALLY DROP THROUGH THE NIGHT WHICH WILL
CREATE A DECENT TEMPERATURE GRADIENT BETWEEN THE LAKE AND THE
LOWER LEVELS OF THE ATMOSPHERE. THIS SHOULD ALSO LEAD TO THE LOW
LEVEL INVERSION BEING PUSHED FURTHER HIGHER TO UP AROUND 4KFT
WHICH WOULD BE SUFFICIENT ENOUGH FOR LAKE EFFECT CLOUDS/PRECIP TO
DEVELOP. WITH NORTH-NORTHEASTERLIES ACROSS THE ENTIRE LAKE...THERE
WILL BE SUFFICIENT FETCH FOR A DECENT CONVERGENT BAND TO DEVELOP
AND TAKE AIM ON SE WISCONSIN AND NE ILLINOIS FRIDAY NIGHT AND
EVENTUALLY SWING EASTWARD ALONG THE SOUTHERN RIM OF THE LAKE
THROUGH SATURDAY NIGHT. STILL TOO FAR TO PIN DOWN ANY SNOWFALL
TOTALS...BUT A COUPLE INCHES DOESNT SEEM OUT OF THE QUESTION ALONG
THE LAKE.
ONE OF KEY FACTORS FOR THE LES DEVELOPMENT IS THE COLD AIR
STREAMING DOWN FROM CANADA. TEMPERATURES WILL END UP IN THE
SINGLE DIGITS FRIDAY MORNING ACROSS THE MOST REGION...WITH THE
COLDEST SURGE OF 850MB TEMPS OF -15 TO -18C AIR COMING DOWN ON
SATURDAY MORNING WHICH WILL ACCOMPANY THE 1030MB SFC HIGH. AFTER
TEMPS BOTTOM OUT SATURDAY MORNING...THINGS WILL BE IMPROVING INTO
SUNDAY AND PARTICULARLY INTO THE EARLY HALF OF THE WORK WEEK. NO
REAL WEATHER SYSTEMS ON THE HORIZON AFTER THE LAKE EFFECT EVENT
BUT TEMPERATURES WILL BE AT LEAST GETTING BACK TO NORMAL...WHICH
IS AROUND 40 FOR A HIGH...AND HIGHER. WENT ABOVE GUIDANCE A BIT
MONDAY THROUGH WEDNESDAY WITH A WARM FRONT MOVING THROUGH THE
REGION WEDNESDAY THAT SHOULD BRING US INTO THE 50S OR POSSIBLY
HIGHER IF THE FORECAST CAN HOLD TRUE.
HALBACH
&&
.AVIATION...
614 PM CST
RE 00Z TAFORS...MID LEVEL SHORT WAVE TROUGH OVER WESTERN WI AND
ALONG THE IA-IL BORDER ROTATING EASTWARD FORECAST TO MOVE TO SE
WI AND NE IL BY 06Z. AIRCRAFT SOUNDINGS SHOW THAT NAM MODEL
FORECAST WITH DRY AIR BELOW 750MB VERIFIES MUCH BETTER THAN GFS
NEAR SATURATED LOW LEVELS. NAM SHOWED WEAK MID LEVEL ISENTROPIC
UPGLIDE ACROSS SOUTHERN WI AND FAR NORTHERN IL AT 18Z...WHICH IS
WHERE THE SIGNIFICANT SN WAS/IS OCCURRING. THIS AREA OF LIFT
FORECAST TO MOVE E TO SOUTHERN LOWER MI AT 00Z AHEAD OF THE SHORT
WAVE TROUGH. TIMING A LITTLE QUICK BUT POSITIONING GOOD SO EXPECT
IN ANY -SN OBSERVED AT TERMINALS IT WILL BE INCONSEQUENTIAL EXCEPT
FOR AT KRFD WHERE LIKELY TO DROP VSBY TO MVFR EARLY THIS EVENING
UNTIL THE SHORT WAVE TROUGH PASSES.
AS SHORT WAVE MOVES E SO DOES COLD FRONT WHICH IS CURRENTLY INTO
WESTERN WI...EASTERN IA...FAR W CENTRAL IL. WIDESPREAD STRATOCU
BEHIND THE FRONT EXPECTED TO CONTINUE TO SPREAD E WITH THE FRONT.
WSHFT EXPECTED AT KRFD AROUND 03Z AND ACROSS CHI VC AROUND 06Z
WITH PREVAILING MVFR CIGS AN HOUR OR TWO FOLLOWING FROPA.
AS SOUTHERN PORTION OF SURFACE RIDGE BUILDS SSE ACROSS THE UPPER
MIDWEST INTO THE MID MS VALLEY DURING THU THE LOW LEVEL FLOW
BECOMES ANTICYCLONIC AND SHOULD SEE CEILINGS SCATTER OUT BY MIDDAY.
TRS
&&
.MARINE...
211 PM...WEAK HIGH PRESSURE OVER THE WESTERN LAKES AND OH VALLEY
WILL MOVE EAST TO THE MID ATLANTIC STATES TONIGHT. LOW PRESSURE
JUST NORTH OF LAKE SUPERIOR WILL MOVE EAST INTO QUEBEC THURSDAY
WITH A TRAILING COLD FRONT MOVING EAST ACROSS THE WESTERN LAKES
THURSDAY MORNING. A STRONG AREA OF HIGH PRESSURE WILL MOVE ACROSS
THE NORTHERN PLAINS THURSDAY AND THURSDAY NIGHT...REACHING THE
WESTERN LAKES FRIDAY. AT THE SAME TIME...ANOTHER AREA OF LOW
PRESSURE WILL MOVE NORTHEAST ALONG THE ATLANTIC COAST. THE
PRESSURE GRADIENT WILL TIGHTEN BETWEEN THESE TWO FEATURES OVER
THE WESTERN LAKES FRIDAY AND FRIDAY NIGHT BEFORE RELAXING SATURDAY
INTO SATURDAY NIGHT. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS CHICAGO/ROMEOVILLE IL
615 PM CST WED MAR 5 2008
.DISCUSSION...
302 PM CST
INITIAL FOCUS IS ON THE SNOW CHANCES FOR THIS AFTERNOON INTO THE
NIGHT AS A WEAK CLIPPER SYSTEM CONTINUES ITS PROGRESS INTO
NORTHERN ILLINOIS. SFC LOW CURRENTLY ANALYZED IN SE IOWA WILL
PROPAGATE EASTWARD INTO NORTHERN ILLINOIS TONIGHT AND THEN ON INTO
MICHIGAN BY THURSDAY MORNING. CONCEPTUALLY...THE GFS SEEMS TO HAVE
A BETTER HANDLE ON THE SNOW/PRECIP WITH THIS SYSTEM...WITH THE
BULK OF THE SNOW FALLING JUST TO THE NORTH OF THE TRACK OF THE LOW
AND THE WARM FRONT EXTENDING EAST OUT OF THE LOW. LOOKS LIKE THERE
COULD ALSO BE A QUICK SHOT FOR SOME LIGHT SNOW ALONG AND AHEAD OF
THE COLD FRONT SOUTH OF THE LOW. VISIBILITIES OUT IN EASTERN IOWA
HAVE BEEN AS LOW AS 1/2SM AT TIMES...BUT FOR THE MOST PART HAVE
BEEN IN THE 1 TO 5 MILE RANGE. WITH NOT A LOT OF MOISTURE TO WORK
WITH...LIKELY WONT SEE MUCH ACCUMULATION OUT OF THIS WITH A
DUSTING TO A HALF INCH MOST LIKELY. HIGHER AMOUNTS WILL LIKELY
STAY NORTH OF THE GREAT WEATHER DIVIDER IN NORTHERN ILLINOIS KNOWN
AS I-80. ALL THIS SAID...CONFIDENCE IS LOW IN HOW MUCH SNOW WILL
FALL DUE TO THE WEAK NATURE OF THIS SFC LOW AND THERE REALLY BEING
NO STRONG FOCUS WITH THE LOW...BUT IT DOES LOOK LIKE WE WILL AT
LEAST SEE SOME FLAKES.
AFTER THIS SYSTEM MOVES OUT OF THE REGION...A REINFORCING SHOT OF
COLD AIR WILL DROP DOWN ON THURSDAY NIGHT. ALONG THE LEADING EDGE
OF THE COLD AIR...SOME SCATTERED FLURRIES WILL BE POSSIBLE. THE
GFS IS TRYING TO PUMP OUT SOME MEASURABLE PRECIP...BUT CURRENT
THINKING IS THAT IT IS OVERDOING IT A BIT. THIS COLD AIR WILL SET
THE STAGE FOR THE NEXT CHANCES FOR SNOW ACROSS NE IL/NW IN.
SETUP SEEMS FAVORABLE FOR LAKE EFFECT SNOW STARTING FRIDAY NIGHT
AS A LOW PRESSURE SYSTEM RAMPS UP IN THE SOUTHERN US AND A 1038MB
HIGH PUSHES DOWN ACROSS THE UPPER MISSISSIPPI RIVER VALLEY REGION.
850MB TEMPS WILL CONTINUALLY DROP THROUGH THE NIGHT WHICH WILL
CREATE A DECENT TEMPERATURE GRADIENT BETWEEN THE LAKE AND THE
LOWER LEVELS OF THE ATMOSPHERE. THIS SHOULD ALSO LEAD TO THE LOW
LEVEL INVERSION BEING PUSHED FURTHER HIGHER TO UP AROUND 4KFT
WHICH WOULD BE SUFFICIENT ENOUGH FOR LAKE EFFECT CLOUDS/PRECIP TO
DEVELOP. WITH NORTH-NORTHEASTERLIES ACROSS THE ENTIRE LAKE...THERE
WILL BE SUFFICIENT FETCH FOR A DECENT CONVERGENT BAND TO DEVELOP
AND TAKE AIM ON SE WISCONSIN AND NE ILLINOIS FRIDAY NIGHT AND
EVENTUALLY SWING EASTWARD ALONG THE SOUTHERN RIM OF THE LAKE
THROUGH SATURDAY NIGHT. STILL TOO FAR TO PIN DOWN ANY SNOWFALL
TOTALS...BUT A COUPLE INCHES DOESNT SEEM OUT OF THE QUESTION ALONG
THE LAKE.
ONE OF KEY FACTORS FOR THE LES DEVELOPMENT IS THE COLD AIR
STREAMING DOWN FROM CANADA. TEMPERATURES WILL END UP IN THE
SINGLE DIGITS FRIDAY MORNING ACROSS THE MOST REGION...WITH THE
COLDEST SURGE OF 850MB TEMPS OF -15 TO -18C AIR COMING DOWN ON
SATURDAY MORNING WHICH WILL ACCOMPANY THE 1030MB SFC HIGH. AFTER
TEMPS BOTTOM OUT SATURDAY MORNING...THINGS WILL BE IMPROVING INTO
SUNDAY AND PARTICULARLY INTO THE EARLY HALF OF THE WORK WEEK. NO
REAL WEATHER SYSTEMS ON THE HORIZON AFTER THE LAKE EFFECT EVENT
BUT TEMPERATURES WILL BE AT LEAST GETTING BACK TO NORMAL...WHICH
IS AROUND 40 FOR A HIGH...AND HIGHER. WENT ABOVE GUIDANCE A BIT
MONDAY THROUGH WEDNESDAY WITH A WARM FRONT MOVING THROUGH THE
REGION WEDNESDAY THAT SHOULD BRING US INTO THE 50S OR POSSIBLY
HIGHER IF THE FORECAST CAN HOLD TRUE.
HALBACH
&&
.AVIATION...
614 PM CST
RE 00Z TAFORS...MID LEVEL SHORT WAVE TROUGH OVER WESTERN WI AND
ALONG THE IA-IL BORDER ROTATING EASTWARD FORECAST TO MOVE TO SE
WI AND NE IL BY 06Z. AIRCRAFT SOUNDINGS SHOW THAT NAM MODEL
FORECAST WITH DRY AIR BELOW 750MB VERIFIES MUCH BETTER THAN GFS
NEAR SATURATED LOW LEVELS. NAM SHOWED WEAK MID LEVEL ISENTROPIC
UPGLIDE ACROSS SOUTHERN WI AND FAR NORTHERN IL AT 18Z...WHICH IS
WHERE THE SIGNIFICANT SN WAS/IS OCCURRING. THIS AREA OF LIFT
FORECAST TO MOVE E TO SOUTHERN LOWER MI AT 00Z AHEAD OF THE SHORT
WAVE TROUGH. TIMING A LITTLE QUICK BUT POSITIONING GOOD SO EXPECT
IN ANY -SN OBSERVED AT TERMINALS IT WILL BE INCONSEQUENTIAL EXCEPT
FOR AT KRFD WHERE LIKELY TO DROP VSBY TO MVFR EARLY THIS EVENING
UNTIL THE SHORT WAVE TROUGH PASSES.
AS SHORT WAVE MOVES E SO DOES COLD FRONT WHICH IS CURRENTLY INTO
WESTERN WI...EASTERN IA...FAR W CENTRAL IL. WIDESPREAD STRATOCU
BEHIND THE FRONT EXPECTED TO CONTINUE TO SPREAD E WITH THE FRONT.
WSHFT EXPECTED AT KRFD AROUND 03Z AND ACROSS CHI VC AROUND 06Z
WITH PREVAILING MVFR CIGS AN HOUR OR TWO FOLLOWING FROPA.
AS SOUTHERN PORTION OF SURFACE RIDGE BUILDS SSE ACROSS THE UPPER
MIDWEST INTO THE MID MS VALLEY DURING THU THE LOW LEVEL FLOW
BECOMES ANTICYCLONIC AND SHOULD SEE CEILINGS SCATTER OUT BY MIDDAY.
TRS
&&
.MARINE...
211 PM...WEAK HIGH PRESSURE OVER THE WESTERN LAKES AND OH VALLEY
WILL MOVE EAST TO THE MID ATLANTIC STATES TONIGHT. LOW PRESSURE
JUST NORTH OF LAKE SUPERIOR WILL MOVE EAST INTO QUEBEC THURSDAY
WITH A TRAILING COLD FRONT MOVING EAST ACROSS THE WESTERN LAKES
THURSDAY MORNING. A STRONG AREA OF HIGH PRESSURE WILL MOVE ACROSS
THE NORTHERN PLAINS THURSDAY AND THURSDAY NIGHT...REACHING THE
WESTERN LAKES FRIDAY. AT THE SAME TIME...ANOTHER AREA OF LOW
PRESSURE WILL MOVE NORTHEAST ALONG THE ATLANTIC COAST. THE
PRESSURE GRADIENT WILL TIGHTEN BETWEEN THESE TWO FEATURES OVER
THE WESTERN LAKES FRIDAY AND FRIDAY NIGHT BEFORE RELAXING SATURDAY
INTO SATURDAY NIGHT. CMS
&&
.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&
$$
AREA FORECAST DISCUSSION...UPDATED FOR AVIATION
NWS MARQUETTE MI
120 PM EST WED MAR 5 2008
.DISCUSSION...
00Z RAOBS/LATEST WV IMAGERY AND RUC ANALYSIS SHOW SPLIT FLOW ACRS
NAMERICA WITH THE UPR LKS UNDER POLAR BRANCH BTWN ARCTIC BRANCH
TROFFING IN CNTRL CAN AND STRONGER...MORE ZONAL SRN BRANCH FLOW OVER
THE SRN STATES. SFC HI PRES RDG EXTENDING WSW FM CENTER OVER QUEBEC
INTO THE UPR LKS IS BRINGING A TRANQUIL OVERNGT TO THE FA WITH 00Z
GRB RAOB/01Z TAMDAR SDNG FM SAW SHOWING A DRY AIRMASS WITH LO
SUBSIDENCE INVRN BASE H9-915. LOOKING UPSTREAM...POLAR BRANCH SHRTWV
NOTED OVER NRN MN...AND MID CLD IN ADVANCE OF THIS FEATURE IS
SPILLING INTO THE FA. BUT DRY LLVLS SHOWN ON THE 00Z INL/MPX RAOBS
AND TAMDAR SDNG FM DLH IS GREATLY LIMITING ASSOCIATED SN INTENSITY/
COVG ACRS NE MN. ALTHOUGH LLVLS SHOWN ON THE 00Z ABR SDNG ARE ALSO
RATHER DRY...A BIT MORE SN IS NOTED OVER SW MN IN ADVANCE OF ANOTHER
POLAR BRANCH SHRTWV/UNDER AREA OF ACCOMPANYING UPR DVGC MOVING ENEWD
THRU NEBRASKA THAT IS IN RRQ OF H3 JET AXIS EXTENDING WSW FM 150KT
H3 JET MAX IN QUEBEC WHERE UPR CONFLUENCE BTWN BRANCHES IS MORE
IMPRESSIVE. ANOTHER FEATURE OF INTEREST IS ARCTIC BRANCH SHRTWV
DIGGING SEWD THRU SCNTRL CAN. ACCOMPANYING SFC-H85 ARCTIC FNT IS
PUSHING THRU THE DAKOTAS/NW MN EARLY THIS MRNG. AIRMASS BEHIND THE
FNT IS QUITE DRY PER 00Z YQD SDNG/SFC DWPTS FALLING TOWARD -15F.
MAIN FCST CONCERNS THIS PACKAGE ARE SN CHCS/AMTS TDAY ASSOCIATED
WITH POLAR BRANCH SHRTWV COMPLEX UPSTREAM AND THEN TRANSITION TO LES
BEGINNING TNGT AS ARCTIC BRANCH SURGES INTO THE GRT LKS.
FOR TDAY...SHRTWV NOW OVER NRN MN FCST BY NAM/GFS TO SHEAR OUT TO
THE NE WHILE SYS NOW MOVING THRU NE IS PROGGED TO DRIFT INTO WI AND
THEN NRN LK MI THIS AFTN. UPR DVGC/H85-5 QVECTOR CNVGC/H7 UVV AHEAD
OF THIS FEATURE AND IN RRQ OF H3 JET AXIS EXTENING BACK INTO THE WRN
GRT LKS (AND AIDED BY THE SHARPENING TEMP GRADIENT WITH APRCHG
ARCTIC FNT) IS FCST TO IMPACT THE WRN ZNS THIS MRNG BEFORE SHIFTING
TO THE NE LATE IN THE DAY FOLLOWING EXIT OF UPR JET AXIS/SHRTWV INTO
NRN LWR MI. DESPITE THESE DYNAMICS...THINK THE GFS IS MORE ON TRACK
WITH A SLOWER ARRIVAL OF PCPN THAN THE NAM DUE TO DRY NATURE OF
LLVLS IN ADVANCE OF THE DYNAMICS. BUT GFS FCST SDNGS SHOW LLVLS
MOISTENING THRU THE DAY...SO PREFER THE HIER NAM MOS POPS...
ESPECIALLY GIVEN FAIRLY WDSPRD NATURE OF SN NOW IN SW MN THAT SHOULD
OVERSPREAD THE FA W-E. WL CARRY LOWER CHC POPS OVER THE E/SE BECAUSE
BETTER UPR DYNAMICS EXIT AFT 18-21Z AND WHERE GFS FCST SDNGS SHOW
MORE RESILIENT LLVL DRY AIR. OTRW...ARRIVAL OF ARCTIC COLD FNT LATE
OVER THE W WL OFFER A CHC AT INCRSD POPS THERE EVEN FOLLOWING
DEPARTURE OF SHARPER SHRTWV/JET DYNAMICS. AS FAR AS SN AMTS ARE
CONCERNED... GFS SHOWS FAIRLY SHARP UVV WITHIN 5K FT DEEP GOOD SN
GROWTH LYR. WOULD USE A 20:1 SN/WATER RATIO...BUT WL CUT BACK A BIT
TO ACCOUNT FOR LLVL DRY LYR THAT WL HAVE TO BE OVERCOME. WITH A QPF
ARND 0.10 INCH...SUSPECT AN AVERAGE OF 1.5 INCHES WL FALL W OF
MQT-IMT WITH LESSER AMTS TO THE E.
ARCTIC FNT FCST TO MOVE ACRS THE FA TNGT...REACHING ERY ARND 09Z OR
SO. ALTHOUGH SHARPER DYNAMICS WL BE GONE BY 00Z...GUIDANCE SHOWS
DEEP MSTR DEPARTING ONLY SLOWLY AHEAD OF THE FROPA. SO SCT -SHSN WL
CONTINUE THRU THE EVNG ACRS THE ENTIRE FA AND UNTIL FROPA. FOLLOWING
THE FROPA...ACTIVITY WL TRANSITION TO PURE LES IN THE NW WIND SN
BELTS AND TEND TO END ELSEWHERE AS LLVLS WITHIN THE ARCTIC AIRMASS
ARE QUITE DRY. THERE COULD BE A PD OF ENHANCED SN IN THE EVNG OVER
THE W AS FNT ARRIVES WHILE GFS FCST SHOW MSTR EXTENDING TO H75. IN
THE PURE LES REGIME THAT FOLLOWS THE DEPARTURE OF THE MSTR...LES
CHART SUGS 3-6"/12HRS. BUT DRY NATURE OF AIRMASS...DCRSG SN GROWTH
QUALITY WITH SURGE OF H85 TEMPS FALLING BLO -20C AND ICE COVERAGE
OVER WRN LK SUP WL NEGATIVELY IMPACT SN AMTS AND HOLD TOTALS BLO
CHART FCST. THERE MAY ALSO BE A BRIEF PD OF LK ENHANCED SN OVER THE
E IN THE NW SN BELTS WITH ARRIVAL OF THE FNT BEFORE DEPARTURE OF
DEEP MSTR...BUT THIS WL BE LATE.
AS ARCTIC BRANCH TROF AMPLIFIES INTO THE GRT LKS DURING THE LATE
WEEK PD...COLDER AIR WILL CONTINUOUSLY POUR INTO THE FA...GENERATING
LES. GFS/UKMET SHOW H85 TEMPS VARYING FM -20C AT ERY TO -24C AT IWD
AT 00Z FRI. GFS SHOWS H85 TEMPS BOTTOMING OUT AS LO AS -28C OVER THE
W AT 12Z FRI...BUT UKMET IS A BIT MORE CONSERVATIVE WITH -26C.
ALTHOUGH THESE MODELS SHOW THE LLVL FLOW VEERING MORE NNW WITH TIME
AS THE ARCTIC HI PRES CENTER REACHES SRN MN BY 00Z SAT...EXPECT THIS
LES EVENT TO BE PREDOMINANTLY A NW SN BELTS EVENT. OTRW...DRYNESS OF
AIRMASS...INCRSGLY NEGATIVE SN GROWTH WITH ARRIVAL OF EVER COLDER
AIR...SFC HTG OVER LAND DURING THE DAY...AND LOWERING INVRN BASE WL
TEND TO LIMIT SN AMTS BLO THAT SUGGESTED BY LES CHART...GOING UP TO
3"/12 HRS SEEMS APPROPRIATE FOR EXPECTED CONDITIONS. THERE MAY BE A
PD OF SOMEWHAT HEAVIER LES THU EVNG AS GFS/UKMET SHOW A REINFORCING
SHRTWV SWINGING THRU THE UPR LKS...WITH FCST INVRN BASE ON GFS FCST
SDNGS RISING TO ARND 7K FT AT CMX WITH SOME MID LVL MOISTENING.
GFS IS THE MOST PROGRESSIVE WITH BLDG SFC RDG INTO THE UPR LKS ON
SAT...BUT 00Z CNDN/ECMWF SHOW MORE UPR TROF AMPLIFICATION AND THE
RETURN OF A MORE NLY CYC FLOW ON THE WRN FLANK OF DEEPENING LO OVER
THE ERN STATES AS EARLY AS FRI NGT. SO WL MAKE NO CHGS IN THE WX FOR
FRI NGT/SAT AS NCEP PREFERS CNDN/ECMWF DEPICTION EXCEPT TO LOWER
POPS A BIT OVER THE FAR W WHERE EVEN THE CNDN/ECMWF SHOW MORE ACYC
FLOW.
AS FOR TEMPS...TENDED TO LOWER GOING FCST HI TEMPS A FEW DEGREES TO
MATCH MIXING TO H85 ON GFS FCST SDNGS. ALSO LOWERED FCST MIN TEMPS
OVER THE INTERIOR W HALF THRU THE FCST WITH EXPECTATION OF MORE WNW
FLOW/LESS LK MODIFICATION. TEMPS LOOK LO ENUF THU NGT TO BE
CONCERNED ABOUT WIND CHILL HEADLINES WITH ARRIVAL OF H85 THERMAL
TROF...BUT WIND SPEEDS MAY NOT BE HI ENUF TO JUSTIFY A HEADLINE
WHERE TEMPS WL BE LOWEST OVER THE INTERIOR W HALF.
&&
.AVIATION (FOR THE 18Z TAF ISSUANCE)...
-SN GRADUALLY MOVING E ACROSS UPPER MI AND WI AHEAD OF APPROACHING
FRONT...WHICH WAS MAINLY PRODUCING MVFR TO OCCASIONAL IFR CONDITIONS
ACROSS THE AREA. THEREFORE...HAVE MVFR COND FOR KSAW THIS AFTN WITH
TEMPO IFR AS STRONGER -SN MOVES EAST ACROSS CENTRAL UP. -SN SHOULD
DIMINISH TONIGHT AS FRONT EXITS THE AREA AND LK EFFECT SNOW
DEVELOPS. HAVE LIMITED THE MENTION OF -SN AT KSAW AFTER 08Z...AS
WINDS ARE AT A WNW DIRECTION...WHICH SHOULD KEEP THE STRONGEST SNOW
ALONG THE LAKE SHORE AREAS OVERNIGHT AND TOMORROW. AT KCMX...KEPT
MVFR CEILINGS IN FOR THIS AFTERNOON...AS LK EFFECT CLOUDS LOOKED TO
BE DEVELOPING OVER THE ICE FREE AREAS OF LK SUPERIOR ON VIS
SAT...BUT DID DIMINISH THE VSBY REDUCTIONS FROM THE -SN AS DRIER AIR
ALOFT WORKS INTO THE THE AREA ALONG AND BEHIND THE FRONT. EXPECT THE
LK EFFECT SNOW TO DEVELOP THIS EVENING...AS COLDER AIR AND NW WINDS
MOVE OVER THE KEWEENAW. DID ADD A TEMPO LATE THIS EVENING OF IFR
VSBY FOR THE EXPECTED TIME OF THE STRONGEST LK EFFECT.
OTHERWISE...MVFR CONDITIONS ARE EXPECTED OVERNIGHT AND THURS MORNING
AS LK EFFECT CONTINUES.
&&
.MARINE (FOR THE 4 AM LAKE SUPERIOR FORECAST ISSUANCE)...
NEXT ROUND OF STRONGER WINDS (FREQUENTLY 20-30KT) AND HEAVY FREEZING
SPRAY WILL ARRIVE TONIGHT THRU FRI FOR THE WEST HALF AS ANOTHER
ARCTIC AIRMASS DROPS SE INTO THE GREAT LAKES REGION. ANOTHER LOW
PRESSURE SYSTEM WILL DROP OUT OF CENTRAL CANADA INTO THE UPPER GREAT
LAKES BY LATE SATURDAY.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...
HEAVY FREEZING SPRAY WARNING FROM 1 AM THURSDAY TO 7 PM EST FRIDAY
FOR LSZ0162>264.
LAKE MICHIGAN...NONE.
&&
$$
DISCUSSION...KC
AVIATION...SRF
MARINE...DLG
AREA FORECAST DISCUSSION
NWS GAYLORD MI
1239 PM EST WED MAR 5 2008
.AVIATION...DRY AIR/CLEAR SKIES/VFR CONDITIONS FOR THE START OF
THE TAF PERIOD WILL TURN VFR CLOUDY THIS AFTERNOON AHEAD OF WEAK
LOW PRESSURE SLIDING EAST TOWARD NRN MICHIGAN. CIGS WILL GRADUALLY
LOWER INTO THE EVENING WITH A PERIOD OF LIGHT SNOW EXPECTED MAINLY
AT TVC AND APN TONIGHT...AS A SFC COLD FRONT APPROACHES. AIR GETS
COLD ENOUGH FOR MINOR LAKE EFFECT INTO TOMORROW...PARTICULARLY
FOR TVC. CONDITIONS INTO THE EVENING WILL BECOME MVFR WITH
TEMPORARY IFR WITH THE LIGHT SNOW.
&&
.PREV DISCUSSION... /ISSUED 1138 AM EST WED MAR 5 2008/
UPDATE...SFC/RUC/SATELLITE/RADAR AND UPPER AIR ANALYSIS SHOWING
QUITE THE CHAOTIC PATTERN. ONE SYSTEM HAS BEEN LIFTING EAST OF THE
REGION THIS MORNING...WHILE WEAK SFC HIGH PRESSURE TRIES TO SETTLE
INTO THE REGION. FURTHER UPSTREAM...WEAK LOW PRESSURE NORTH OF
LAKE SUPERIOR...ASSOCIATED WEAK ISENTROPIC ASCENT IN THE 280-285K
LAYER...AND MODEST HIGH LEVEL (H5-H3) -DIVQ ACROSS CENTRAL
UPPER...HAS RESULTED IN COOLING CLOUD TOPS AND SOME LIGHT SNOW
DEVELOPMENT. THIS LIGHT SNOW HAS HAD TO OVERCOME QUITE THE DRY
LAYER BELOW 8-10KFT SEEN 12Z APX SOUNDING. AREA TAMDAR SOUNDINGS
SHOWING THAT THE FORCING HAS OVERCOME THE DRY AIR MASS ACROSS
WISCONSIN/IOWA AND CENTRAL UPPER.
ALSO...POTENT LITTLE SHORTWAVE LIFTING ENE OUT OF IOWA HAS
RESULTED IN ANOTHER AREA OF COOLING CLOUD TOPS...DUE TO SECONDARY
AREA OF MODEST H5-H7 -DIVQ AND WEAK H3-H2 UPPER DIVERGENCE FROM
LEFT EXIT REGION OF 110KT JET ACROSS ILLINOIS. THIS FEATURE WAS
WORKING AGAINST THE DRY AIR AS WELL...BUT WAS WINNING OUT. THIS
SHORTWAVE WILL TRACK ACROSS AREAS MAINLY SOUTH OF M-72 THIS
AFTERNOON AND MAY ALLOW FOR SOME PATCHY LIGHT SNOWS TO FALL LATE
THIS AFTERNOON.
THE AIR MASS WILL BECOME SATURATED ACROSS UPPER MICHIGAN THIS
AFTERNOON...AND LIGHT SNOWS WILL BECOME LIKELY INTO THE EVENING
HOURS...AS SFC LOW AND ASSOCIATED TROUGH AXIS SWEEP INTO NRN
MICHIGAN. AS THIS TROUGH AXIS WORKS INTO NRN LOWER LATE THIS
EVENING AND OVERNIGHT...A PERIOD OF THESE LIGHT SNOWS WILL DEVELOP
ACROSS MUCH OF THE AREA...WHILE COOLING TEMPERATURES BEHIND THE
FRONT MAY ALLOW THE LAKES TO GET INVOLVED LATE TONIGHT.
ALL-IN-ALL...LITTLE IN THE WAY OF ACCUMULATIONS FOR THIS
AFTERNOON...AND EVEN INTO TONIGHT. MAYBE AN INCH OF SNOW FOR
PORTIONS OF NRN MICHIGAN TONIGHT...BUT THIS WILL GENERALLY BE
NUISANCE STUFF THAT HAS LITTLE TRAVEL/DRIVING IMPACTS ON THE
REGION.
SMD
SYNOPSIS...WEAK LOW PRESSURE AND SURFACE COLD FRONT WILL SWEEP
ACROSS THE REGION TONIGHT...AND HIGH PRESSURE WILL WORK INTO THE
WESTERN GREAT LAKES FRIDAY. MEANWHILE...A STRONG STORM SYSTEM WILL
DEVELOP ACROSS THE GULF COAST STATES FRIDAY AND LIFT NORTHEAST
ACROSS THE APPALACHIANS INTO SATURDAY.
PREV DISCUSSION... /ISSUED 619 AM EST WED MAR 5 2008/
AVIATION...PERIOD OF QUIETER WX TO COME TO AN END. MID CLOUDS ARE
MOVING INTO THE REGION FROM THE WEST...IN ADVANCE OF A TROF OF LOW
PRESSURE IN THE UPPER MS VALLEY. CIGS WILL REMAIN VFR THRU
EVENING...LOWERING FROM 10-15K FT TO AROUND 4K FT IN THE EVENING.
SOME LIGHT SNOW IS POSSIBLE THIS EVENING...WITH A BETTER CHANCE
AFTER MIDNIGHT IN TVC/PLN (WITH ACCOMPANYING MVFR CIGS/VSBYS).
JZ
DISCUSSION...995MB LOW PRESSURE LIFTING ACROSS PA THIS MORNING...
WITH ASSOCIATED PRECIP STRUGGLING TO GET NORTH OF I-69. CIRRUS
SHIELD HAS BACKED UP OVERHEAD...WHICH HAS ALLOWED TEMPS TO REBOUND A
BIT OVER THE LAST FEW HOURS. SURFACE RIDGING...CURLING FROM QUEBEC
TO SUPERIOR TO MISSOURI...IS HELPING KEEP PRECIP AT BAY. THIS RIDGE
SEPARATES THE BIG STORM FROM A 2ND LOW IN EASTERN NEBRASKA. AN
INVERTED TROF EXTENDS NNE FROM THIS LOW INTO MN AND FAR WESTERN
ONTARIO. THE EVOLUTION OF THIS FEATURE...AND ASSOCIATED PRECIP
CHANCES...IS THE MAIN CONCERN IN THE NEAR TERM.
MODELS...ARE DOING DECENTLY INTO THURSDAY. GFS/NAM SHARPLY DIVERGE
AFTER THAT...WITH THE NAM GOING SOMEWHAT SLOWER AND FAR LOWER
HEIGHTS WITH THE UPPER TROFFING EXTENDING INTO THE LAKES REGION. THE
REST OF THE MODEL SUITE DIGS ENERGY MUCH FURTHER SOUTHWARD...THOUGH
THE GFS PROBABLY DOESN/T LOWER HEIGHTS ENOUGH. 12Z ECMWF/00Z
CANADIAN OFFER DECENT COMPROMISE SOLUTIONS BY THE TIME WE REACH THE
WEEKEND.
TODAY...THE SURFACE LOW NOW IN NEBRASKA SHOULD SPIN DOWN...REPLACED
BY A WEAK SURFACE LOW ALONG THE INVERTED TROF ON LAKE SUPERIOR.
PERSISTENT (THOUGH WEAK) 285K ISENTROPIC ASCENT WILL AID IN
GRADUALLY MOISTENING THE MID AND UPPER LEVELS. HOWEVER...THE LOW
LEVEL ARE AND WILL REMAIN DRY MUCH LONGER...WITH VERY DRY ANTECEDENT
AIR AND ONLY WEAK FORCING ABOVE. THE GFS REMAINS A LITTLE FASTER AT
OVERCOMING THE LOW LEVEL DRY AIR...BUT THE MODELS ARE CLOSER...AND
IN GENERAL CONTINUE TO INDICATE A RATHER SLOW ONSET OF SNOW. WILL
HOLD OFF ON ANY PRECIP UNTIL AFTER 4 PM...AND THEN BREAK OUT A
CHANCE OF SNOW IN EASTERN UPPER MI AND PARTS OF THE IMMEDIATE NW
LOWER MI COAST. OTHERWISE...INCREASING CLOUDS BUT DRY WX IS
EXPECTED. MAX TEMPS STRUGGLED MIGHTILY ON TUESDAY...DESPITE FULL
EARLY MARCH SUN. WITH THAT IN MIND...WILL STEER A BIT BELOW
GUIDANCE...WITH HIGHS IN THE UPPER 20S TO AROUND 30.
TONIGHT...WEAK SURFACE LOW WILL MAINTAIN INTENSITY AS IT DRIFTS
EASTWARD...TO JUST EAST OF SUPERIOR. AN ASSOCIATED COLD FRONT WILL
MOVE THRU EASTERN UPPER/NW LOWER MI OVERNIGHT. THIS IS OCCURRING IN
ADVANCE OF AN ARCTIC SHORTWAVE...DIGGING TOWARD NORTHERN MN. 285K
ISENTROPIC ASCENT IS ONLY SLIGHTLY STRONGER THAN THE DAYLIGHT HOURS
(PEAKING 06Z-09Z). HOWEVER...PART OF THE WORK OF OVERCOMING LOW
LEVEL DRY AIR HAS ALREADY BEEN DONE...SO THE RESULT WILL BE A BETTER
CHANCE FOR SNOW. LAKE ENHANCEMENT COULD ASSIST THINGS VERY LATE...AS
850MB TEMPS DROP TO THE LOWER MINUS TEENS ON THE BACK EDGE OF THE
DEEPER MOISTURE SHIELD. WILL HAVE A CHANCE OF LIGHT SNOW ACROSS THE
AREA TONIGHT...AND WILL UP TO LOW LIKELY POPS ON THE LAKE MI COAST
OF NW LOWER...TO ABOUT 2 COUNTIES INLAND (AS WELL AS WESTERN
CHIPPEWA CO). NEITHER FORCING NOR INSTABILITY ARE ESPECIALLY
IMPRESSIVE...AND WILL KEEP ACCUMS AT AROUND AN INCH OR LESS. MIN
TEMPS MID TEENS TO AROUND 20.
THURSDAY...SURFACE LOW PULLS AWAY TOWARD WESTERN QUEBEC...WITH
CLASSIC LAKE-INDUCED TROFFING LINGERING BACK ACROSS NORTHERN HURON/
SOUTHERN SUPERIOR. MAIN UPPER TROF AXIS REMAINS UPSTREAM...AS ENERGY
CONTINUE TO DIG INTO THE DAKOTAS AND MN. MIGHT HAVE SOME LINGERING
SYNOPTIC-ASSISTED PRECIP IN THE EAST IN THE MORNING...BUT PURE LAKE
EFFECT SNOW IS THE MAIN CONCERN. 850MB TEMPS WILL LOWER TO AROUND
-20C ON EASTERN SUPERIOR WITH A WNW/NW FETCH...AND -18C ON NORTHERN
LAKE MI ON A W/WNW FETCH DURING THE DAY. WILL INCREASE THE COVERAGE
OF LIKELY POPS...TO INCLUDE MOST OF NW AND N CENTRAL LOWER MI...AND
MOST OF CENTRAL/WESTERN CHIPPEWA CO. EASTERN UPPER MI WILL HAVE THE
LONG SUPERIOR FETCH...AND 850-700MB RH LEVELS 70-80 PERCENT. ACCUMS
OF 1-3 SEEM REASONABLE...HIGHEST OF COURSE NEAR PARADISE/WHITEFISH.
NORTHERN LOWER WILL LACK A SUPERIOR CONNECTION...AND WILL BE DRIER
AT 50-60 PERCENT. AROUND AN INCH LOOKS BETTER IN THE SNOWBELTS SOUTH
OF THE BRIDGE. MAX TEMPS MID 20S TO LOWER 30S...BUT RELATIVELY EARLY
IN THE DAY.
THURSDAY NIGHT...COLDER AIR CONTINUES TO SPILL INTO THE REGION...
WITH 850MB TEMPS LOWERING TOWARD THE LOWER MINUS 20S THU NIGHT...AND
STAYING THERE FRIDAY. 1000-850MB FLOW IS GENERALLY W TO NW BUT
BECOMING RATHER WEAK THU NIGHT AS THE PRESSURE GRADIENT DIMINISHES.
THIS WILL RESULT IN SOME MESOSCALE HEADACHES...ESPECIALLY IN UPPER
MI AS SURFACE NE WINDS WILL LIKELY DEVELOP OFF ON ONTARIO. BUT THIS
IS ALSO WHERE THE BEST LAKE EFFECT POTENTIAL...THANKS AGAIN TO A
LONGER FETCH AND MORE MID-LEVEL MOISTURE. WILL KICK POPS TO LIKELY
THU EVENING IN CHIPPEWA CO...BUT ONLY IN THE FAR WEST OVERNIGHT DUE
TO POTENTIAL DRAINAGE FLOW. 850/700MB RH LEVELS STRUGGLE TO REACH 50
PERCENT ON NORTHERN LAKE MI...AND FEEL COMFORTABLE WITH JUST SCT
SNOW SHOWERS THERE. MIN TEMPS SINGLE DIGITS TO AROUND 10 ABOVE.
FRIDAY...CYCLOGENESIS PROCEEDS IN THE SE STATES...WHILE RIDGING
BUILDS INTO THE UPPER MS VALLEY. 1000-850MB WINDS WILL VEER
NORTHERLY IN RESPONSE...A LESS THAN IDEAL FETCH FOR SNOW. IN
ADDITION...THE 850-700MB LAYER DRIES (GOING TO 50 PERCENT OR LESS
ACROSS THE REGION)...WITH SOME ANTICYCLONIC CURVATURE TRYING TO WORK
IN FROM THE WEST. WILL KEEP A CHANCE OF SNOW SHOWERS GOING...
ESPECIALLY IN NW LOWER AND CHIPPEWA CO. MAX TEMPS UPPER TEENS TO
AROUND 20.
REST OF THE FORECAST...THE HIGH AMPLITUDE UPPER TROF SLOWLY
PROGRESSING INTO THE EAST HALF OF THE COUNTRY WILL CONTRIBUTE TO A
MAJOR STORM SYSTEM THIS WEEKEND...BUT PROBABLY FOR THE EAST COAST.
FOR US...COLD WITH SNOW SHOWERS INITIALLY...WITH GRADUAL RECOVERY IN
TEMPS NEXT WEEK.
ZOLTOWSKI
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
&&
$$
AREA FORECAST DISCUSSION
NWS GAYLORD MI
1138 AM EST WED MAR 5 2008
.UPDATE...SFC/RUC/SATELLITE/RADAR AND UPPER AIR ANALYSIS SHOWING
QUITE THE CHAOTIC PATTERN. ONE SYSTEM HAS BEEN LIFTING EAST OF THE
REGION THIS MORNING...WHILE WEAK SFC HIGH PRESSURE TRIES TO SETTLE
INTO THE REGION. FURTHER UPSTREAM...WEAK LOW PRESSURE NORTH OF
LAKE SUPERIOR...ASSOCIATED WEAK ISENTROPIC ASCENT IN THE 280-285K
LAYER...AND MODEST HIGH LEVEL (H5-H3) -DIVQ ACROSS CENTRAL
UPPER...HAS RESULTED IN COOLING CLOUD TOPS AND SOME LIGHT SNOW
DEVELOPMENT. THIS LIGHT SNOW HAS HAD TO OVERCOME QUITE THE DRY
LAYER BELOW 8-10KFT SEEN 12Z APX SOUNDING. AREA TAMDAR SOUNDINGS
SHOWING THAT THE FORCING HAS OVERCOME THE DRY AIR MASS ACROSS
WISCONSIN/IOWA AND CENTRAL UPPER.
ALSO...POTENT LITTLE SHORTWAVE LIFTING ENE OUT OF IOWA HAS
RESULTED IN ANOTHER AREA OF COOLING CLOUD TOPS...DUE TO SECONDARY
AREA OF MODEST H5-H7 -DIVQ AND WEAK H3-H2 UPPER DIVERGENCE FROM
LEFT EXIT REGION OF 110KT JET ACROSS ILLINOIS. THIS FEATURE WAS
WORKING AGAINST THE DRY AIR AS WELL...BUT WAS WINNING OUT. THIS
SHORTWAVE WILL TRACK ACROSS AREAS MAINLY SOUTH OF M-72 THIS
AFTERNOON AND MAY ALLOW FOR SOME PATCHY LIGHT SNOWS TO FALL LATE
THIS AFTERNOON.
THE AIR MASS WILL BECOME SATURATED ACROSS UPPER MICHIGAN THIS
AFTERNOON...AND LIGHT SNOWS WILL BECOME LIKELY INTO THE EVENING
HOURS...AS SFC LOW AND ASSOCIATED TROUGH AXIS SWEEP INTO NRN
MICHIGAN. AS THIS TROUGH AXIS WORKS INTO NRN LOWER LATE THIS
EVENING AND OVERNIGHT...A PERIOD OF THESE LIGHT SNOWS WILL DEVELOP
ACROSS MUCH OF THE AREA...WHILE COOLING TEMPERATURES BEHIND THE
FRONT MAY ALLOW THE LAKES TO GET INVOLVED LATE TONIGHT.
ALL-IN-ALL...LITTLE IN THE WAY OF ACCUMULATIONS FOR THIS
AFTERNOON...AND EVEN INTO TONIGHT. MAYBE AN INCH OF SNOW FOR
PORTIONS OF NRN MICHIGAN TONIGHT...BUT THIS WILL GENERALLY BE
NUISANCE STUFF THAT HAS LITTLE TRAVEL/DRIVING IMPACTS ON THE
REGION.
SMD
&&
.SYNOPSIS...WEAK LOW PRESSURE AND SURFACE COLD FRONT WILL SWEEP
ACROSS THE REGION TONIGHT...AND HIGH PRESSURE WILL WORK INTO THE
WESTERN GREAT LAKES FRIDAY. MEANWHILE...A STRONG STORM SYSTEM WILL
DEVELOP ACROSS THE GULF COAST STATES FRIDAY AND LIFT NORTHEAST
ACROSS THE APPALACHIANS INTO SATURDAY.
&&
.PREV DISCUSSION... /ISSUED 619 AM EST WED MAR 5 2008/
AVIATION...PERIOD OF QUIETER WX TO COME TO AN END. MID CLOUDS ARE
MOVING INTO THE REGION FROM THE WEST...IN ADVANCE OF A TROF OF LOW
PRESSURE IN THE UPPER MS VALLEY. CIGS WILL REMAIN VFR THRU
EVENING...LOWERING FROM 10-15K FT TO AROUND 4K FT IN THE EVENING.
SOME LIGHT SNOW IS POSSIBLE THIS EVENING...WITH A BETTER CHANCE
AFTER MIDNIGHT IN TVC/PLN (WITH ACCOMPANYING MVFR CIGS/VSBYS).
JZ
DISCUSSION...995MB LOW PRESSURE LIFTING ACROSS PA THIS MORNING...
WITH ASSOCIATED PRECIP STRUGGLING TO GET NORTH OF I-69. CIRRUS
SHIELD HAS BACKED UP OVERHEAD...WHICH HAS ALLOWED TEMPS TO REBOUND A
BIT OVER THE LAST FEW HOURS. SURFACE RIDGING...CURLING FROM QUEBEC
TO SUPERIOR TO MISSOURI...IS HELPING KEEP PRECIP AT BAY. THIS RIDGE
SEPARATES THE BIG STORM FROM A 2ND LOW IN EASTERN NEBRASKA. AN
INVERTED TROF EXTENDS NNE FROM THIS LOW INTO MN AND FAR WESTERN
ONTARIO. THE EVOLUTION OF THIS FEATURE...AND ASSOCIATED PRECIP
CHANCES...IS THE MAIN CONCERN IN THE NEAR TERM.
MODELS...ARE DOING DECENTLY INTO THURSDAY. GFS/NAM SHARPLY DIVERGE
AFTER THAT...WITH THE NAM GOING SOMEWHAT SLOWER AND FAR LOWER
HEIGHTS WITH THE UPPER TROFFING EXTENDING INTO THE LAKES REGION. THE
REST OF THE MODEL SUITE DIGS ENERGY MUCH FURTHER SOUTHWARD...THOUGH
THE GFS PROBABLY DOESN/T LOWER HEIGHTS ENOUGH. 12Z ECMWF/00Z
CANADIAN OFFER DECENT COMPROMISE SOLUTIONS BY THE TIME WE REACH THE
WEEKEND.
TODAY...THE SURFACE LOW NOW IN NEBRASKA SHOULD SPIN DOWN...REPLACED
BY A WEAK SURFACE LOW ALONG THE INVERTED TROF ON LAKE SUPERIOR.
PERSISTENT (THOUGH WEAK) 285K ISENTROPIC ASCENT WILL AID IN
GRADUALLY MOISTENING THE MID AND UPPER LEVELS. HOWEVER...THE LOW
LEVEL ARE AND WILL REMAIN DRY MUCH LONGER...WITH VERY DRY ANTECEDENT
AIR AND ONLY WEAK FORCING ABOVE. THE GFS REMAINS A LITTLE FASTER AT
OVERCOMING THE LOW LEVEL DRY AIR...BUT THE MODELS ARE CLOSER...AND
IN GENERAL CONTINUE TO INDICATE A RATHER SLOW ONSET OF SNOW. WILL
HOLD OFF ON ANY PRECIP UNTIL AFTER 4 PM...AND THEN BREAK OUT A
CHANCE OF SNOW IN EASTERN UPPER MI AND PARTS OF THE IMMEDIATE NW
LOWER MI COAST. OTHERWISE...INCREASING CLOUDS BUT DRY WX IS
EXPECTED. MAX TEMPS STRUGGLED MIGHTILY ON TUESDAY...DESPITE FULL
EARLY MARCH SUN. WITH THAT IN MIND...WILL STEER A BIT BELOW
GUIDANCE...WITH HIGHS IN THE UPPER 20S TO AROUND 30.
TONIGHT...WEAK SURFACE LOW WILL MAINTAIN INTENSITY AS IT DRIFTS
EASTWARD...TO JUST EAST OF SUPERIOR. AN ASSOCIATED COLD FRONT WILL
MOVE THRU EASTERN UPPER/NW LOWER MI OVERNIGHT. THIS IS OCCURRING IN
ADVANCE OF AN ARCTIC SHORTWAVE...DIGGING TOWARD NORTHERN MN. 285K
ISENTROPIC ASCENT IS ONLY SLIGHTLY STRONGER THAN THE DAYLIGHT HOURS
(PEAKING 06Z-09Z). HOWEVER...PART OF THE WORK OF OVERCOMING LOW
LEVEL DRY AIR HAS ALREADY BEEN DONE...SO THE RESULT WILL BE A BETTER
CHANCE FOR SNOW. LAKE ENHANCEMENT COULD ASSIST THINGS VERY LATE...AS
850MB TEMPS DROP TO THE LOWER MINUS TEENS ON THE BACK EDGE OF THE
DEEPER MOISTURE SHIELD. WILL HAVE A CHANCE OF LIGHT SNOW ACROSS THE
AREA TONIGHT...AND WILL UP TO LOW LIKELY POPS ON THE LAKE MI COAST
OF NW LOWER...TO ABOUT 2 COUNTIES INLAND (AS WELL AS WESTERN
CHIPPEWA CO). NEITHER FORCING NOR INSTABILITY ARE ESPECIALLY
IMPRESSIVE...AND WILL KEEP ACCUMS AT AROUND AN INCH OR LESS. MIN
TEMPS MID TEENS TO AROUND 20.
THURSDAY...SURFACE LOW PULLS AWAY TOWARD WESTERN QUEBEC...WITH
CLASSIC LAKE-INDUCED TROFFING LINGERING BACK ACROSS NORTHERN HURON/
SOUTHERN SUPERIOR. MAIN UPPER TROF AXIS REMAINS UPSTREAM...AS ENERGY
CONTINUE TO DIG INTO THE DAKOTAS AND MN. MIGHT HAVE SOME LINGERING
SYNOPTIC-ASSISTED PRECIP IN THE EAST IN THE MORNING...BUT PURE LAKE
EFFECT SNOW IS THE MAIN CONCERN. 850MB TEMPS WILL LOWER TO AROUND
-20C ON EASTERN SUPERIOR WITH A WNW/NW FETCH...AND -18C ON NORTHERN
LAKE MI ON A W/WNW FETCH DURING THE DAY. WILL INCREASE THE COVERAGE
OF LIKELY POPS...TO INCLUDE MOST OF NW AND N CENTRAL LOWER MI...AND
MOST OF CENTRAL/WESTERN CHIPPEWA CO. EASTERN UPPER MI WILL HAVE THE
LONG SUPERIOR FETCH...AND 850-700MB RH LEVELS 70-80 PERCENT. ACCUMS
OF 1-3 SEEM REASONABLE...HIGHEST OF COURSE NEAR PARADISE/WHITEFISH.
NORTHERN LOWER WILL LACK A SUPERIOR CONNECTION...AND WILL BE DRIER
AT 50-60 PERCENT. AROUND AN INCH LOOKS BETTER IN THE SNOWBELTS SOUTH
OF THE BRIDGE. MAX TEMPS MID 20S TO LOWER 30S...BUT RELATIVELY EARLY
IN THE DAY.
THURSDAY NIGHT...COLDER AIR CONTINUES TO SPILL INTO THE REGION...
WITH 850MB TEMPS LOWERING TOWARD THE LOWER MINUS 20S THU NIGHT...AND
STAYING THERE FRIDAY. 1000-850MB FLOW IS GENERALLY W TO NW BUT
BECOMING RATHER WEAK THU NIGHT AS THE PRESSURE GRADIENT DIMINISHES.
THIS WILL RESULT IN SOME MESOSCALE HEADACHES...ESPECIALLY IN UPPER
MI AS SURFACE NE WINDS WILL LIKELY DEVELOP OFF ON ONTARIO. BUT THIS
IS ALSO WHERE THE BEST LAKE EFFECT POTENTIAL...THANKS AGAIN TO A
LONGER FETCH AND MORE MID-LEVEL MOISTURE. WILL KICK POPS TO LIKELY
THU EVENING IN CHIPPEWA CO...BUT ONLY IN THE FAR WEST OVERNIGHT DUE
TO POTENTIAL DRAINAGE FLOW. 850/700MB RH LEVELS STRUGGLE TO REACH 50
PERCENT ON NORTHERN LAKE MI...AND FEEL COMFORTABLE WITH JUST SCT
SNOW SHOWERS THERE. MIN TEMPS SINGLE DIGITS TO AROUND 10 ABOVE.
FRIDAY...CYCLOGENESIS PROCEEDS IN THE SE STATES...WHILE RIDGING
BUILDS INTO THE UPPER MS VALLEY. 1000-850MB WINDS WILL VEER
NORTHERLY IN RESPONSE...A LESS THAN IDEAL FETCH FOR SNOW. IN
ADDITION...THE 850-700MB LAYER DRIES (GOING TO 50 PERCENT OR LESS
ACROSS THE REGION)...WITH SOME ANTICYCLONIC CURVATURE TRYING TO WORK
IN FROM THE WEST. WILL KEEP A CHANCE OF SNOW SHOWERS GOING...
ESPECIALLY IN NW LOWER AND CHIPPEWA CO. MAX TEMPS UPPER TEENS TO
AROUND 20.
REST OF THE FORECAST...THE HIGH AMPLITUDE UPPER TROF SLOWLY
PROGRESSING INTO THE EAST HALF OF THE COUNTRY WILL CONTRIBUTE TO A
MAJOR STORM SYSTEM THIS WEEKEND...BUT PROBABLY FOR THE EAST COAST.
FOR US...COLD WITH SNOW SHOWERS INITIALLY...WITH GRADUAL RECOVERY IN
TEMPS NEXT WEEK.
ZOLTOWSKI
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...NONE.
&&
$$
AREA FORECAST DISCUSSION...UPDATED
NWS MARQUETTE MI
1235 AM EST TUE MAR 4 2008
.SYNOPSIS...
WATER VAPOR IMAGERY AND RUC ANALYSIS SHOW A TROF EXTENDING FROM
HUDSON BAY TO THE CNTRL PLAINS. A COUPLE OF SHORTWAVES ARE NOTED
WITHIN THE TROF. ONE EXTENDS FROM JAMES BAY ACROSS UPPER MI TO IA.
SECOND IS OVER NRN ONTARIO TO THE NW OF LAKE SUPERIOR. UPSTREAM...
NEXT SIGNIFICANT SHORTWAVE IS MOVING ONSHORE OVER THE PACIFIC NW.
THIS SYSTEM WILL HELP KICK A SRN STREAM SHORTWAVE OVER TX TO THE
NE OVER THE NEXT FEW DAYS. CLOSER TO HOME...SFC COLD FRONT HAS
PASSED WELL SE OF THE FCST AREA WITH A DECENT SHOT OF COLD AIR NOW
SETTLING OVER THE UPPER LAKES. 12Z KINL SOUNDING SHOWED 850MB TEMP
OF -18C...9C LWR THAN THE 00Z READING. WITH THE COLD AIR...LES HAS
DEVELOPED. UPSTREAM 12Z KINL SOUNDING ALSO SHOWED A DEEP INVERSION
LAYER BASED AT 890MB (3.3KFT MSL) WITH TEMP AT THE INVERSION BASE
-23C. WHILE INSTABILITY IS STRONG OVER THE LAKE...THE DEEP LOW BASED
INVERSION HAS BEEN A BIG NEGATIVE FACTOR FOR SIGNIFICANT LES. IN
ADDITION...CLEAR SKIES AND FULL DAYTIME HEATING UPWIND OF THE LAKE
HAVE RESULTED IN A WELL MIXED BOUNDARY LAYER (AFTN TAMDAR SOUNDING
FROM CYQT SHOWS THIS NICELY)...ANOTHER NEGATIVE FOR SIGNIFICANT LES.
AS A RESULT...LES HAS SHOWN A DIMINISHING TREND OVER WRN LAKE
SUPERIOR THIS AFTN. AWAY FROM LES...SKIES HAVE COMPLETELY CLEARED
OVER THE W HALF OF UPPER MI.
&&
.SHORT TERM (TONIGHT AND TUESDAY)...
SHORTWAVE NW OF LAKE SUPERIOR WILL PASS N OF THE LAKE THIS EVENING
AND WILL NOT AFFECT LES. OTHERWISE...GIVEN THE NEGATIVES FOR LES
NOTED IN THE SYNOPSIS...NOT EXPECTING MUCH IN THE WAY OF SNOW
ACCUMULATIONS TONIGHT...ESPECIALLY OVER NW UPPER MI WHERE SHORTER
FETCH AND SOME ICE COVER WILL FURTHER LIMIT LES. WOULD BE SURPRISED
TO SEE MORE THAN 1 INCH THERE. TO THE E...LONGER FETCH...SOME
INCREASE IN LOW-LEVEL CONVERGENCE LATER IN THE NIGHT AS LAND BREEZES
STRENGTHEN...AND FAVORABLE DENDRITIC SNOW GROWTH TEMPS BLO THE
INVERSION MAY RESULT IN 1 TO PERHAPS 3 INCHES OF SNOW LOCALLY.
ELSEWHERE...STAGE SHOULD BE SET FOR A COLD NIGHT UNDER CLEAR SKIES.
THERE IS SOME CONCERN THAT STRATOCU OFF LAKE SUPERIOR COULD EXPAND
OVER MORE OF THE FCST AREA LATER IN THE NIGHT AS WINDS JUST BLO
INVERSION BECOME MORE NRLY...BUT WILL ASSUME MUCH OF THE INTERIOR W
HALF WILL REMAIN MOSTLY CLOUD FREE. SFC HIGH PRES DOESN`T ARRIVE
UNTIL VERY LATE IN THE NIGHT...BUT THAT SHOULD STILL BE SUFFICIENT
FOR A FEW HRS OF EXCELLENT RADIATIONAL COOLING...AIDED BY MIN
PRECIPITABLE WATER AROUND 0.10 INCHES (ABOUT 50PCT OF NORMAL). WILL
GO A GOOD 5 DEGREES OR MORE BLO THE COLDEST MOS GUIDANCE IN THE
TYPICAL COLD SPOTS. EXPECT READINGS AROUND -10F OR SO IN THOSE
AREAS.
LINGERING LES SHOULD END TUE AS SFC HIGH PRES PASSES ACROSS THE AREA
AND AIRMASS MODIFIES. MAY SEE LIGHT LES EXPAND OVER NCNRL UPPER MI
FOR A SHORT TIME DURING THE MORNING AS WINDS BECOME NE...BUT
MODIFYING AIRMASS SUGGESTS NOT MUCH MORE THAN FLURRIES.
&&
.LONG TERM (TUESDAY NIGHT THROUGH MONDAY)...
THE CUTOFF LOW FORMING OVER CENTRAL TEXAS THIS AFTERNOON...SHOULD
MOVE TO WESTERN KENTUCKY BY TUESDAY NIGHT...AND THEN MOVE BACK INTO
THE MAIN FLOW AND LARGER SCALE TROUGH LATE TUESDAY NIGHT AND
WEDNESDAY OVER THE LOWER/EASTERN GREAT LAKES. AT THAT
POINT...TROUGHINESS WILL ENCOMPASS MUCH OF INTERIOR CANADA AND THE
UNITED STATES...WITH THE TROUGH AXIS MOVING OVER LAKE SUPERIOR AND
UPPER MICHIGAN FRIDAY.
OUR NEXT WEATHER MAKER WILL BE IN THE FORM OF LOW PRESSURE SKIRTING
OUR WAY FROM THE CENTRAL PLAINS WEDNESDAY NIGHT...SPREADING SNOW
OVER THE AREA LATE WEDNESDAY NIGHT. THE LOW WILL MOVE EAST OF UPPER
MICHIGAN THURSDAY AFTERNOON...RESULTING IN NORTHWESTERLY TO
NORTHERLY WINDS. INITIALLY...LAKE EFFECT SNOW SHOWERS WILL BE
LIMITED. HOWEVER...THEY SHOULD KICK IN AFTER 06Z THURSDAY AS
SURFACE AND TEMPERATURES ALOFT COOL TO -10C OR COLDER.
NORMAL WILL NOT BE THE CASE FOR MUCH OF THE LONG TERM FORECAST AS
HIGH TEMPERATURES AROUND THE 20F DEGREE MARK ARE EXPECTED THURSDAY
THROUGH SATURDAY. NORMAL HIGH TEMPERATURES FOR THIS TIME OF YEAR
ARE GENERALLY IN THE LOW 30S TO RIGHT AROUND 30F AT MQT.
IT LOOKS LIKE MODEL WISE...THINGS ARE ON THE SAME PAGE THROUGH
SATURDAY MORNING AS THE TROUGH AXIS MOVES TO FAR EASTERN ONTARIO
SATURDAY. OF COURSE SOME OF THE SMALLER DETAILS WILL BE AN
ISSUE...BUT THE LARGE SCALE TROUGHS AND RIDGES LOOK TO BE FAIRLY
SIMILAR AT 500MB.
AS A RESULT OF THE DIFFERING MODELS FOR LATE DAY 5/SATURDAY THROUGH
DAY 7/MONDAY...HAVE OPTED TO GO SIMILAR TO HPC GUIDANCE. THIS
RESULTED IN A SWING AWAY FROM THE OPERATIONAL GFS AND MORE TOWARDS
OTHER MODELS AND ENSEMBLES WITH THIS LOW CONFIDENCE
FORECAST...ESPECIALLY WITH THE BREAKDOWN OF THE WEST COAST RIDGE.
BACK TO UPPER MICHIGAN...THIS RESULTED IN A DRY FORECAST FOR
SATURDAY NIGHT ON...AS A LARGE AREA OF HIGH PRESSURE DOMINATES MUCH
OF THE CENTRAL PLAINS STATES SATURDAY THROUGH THE END OF THE WORK
WEEK...BEFORE SHIFTING TO THE EAST COAST.
&&
.AVIATION (FOR THE 06Z TAF ISSUANCE)...
AT KCMX...VEERING LLVL FLOW HAS ADVECTED SOME BKN SC MVFR CIGS INTO
THE KEWEENAW PENINSULA...BUT MVFR CIGS SHOULD TEND TO SCATTER OUT
EARLY THIS MRNG AS SFC HIGH PRES ARRIVES. THEN EXPECT PREVAILING VFR
CONDITIONS TO CONTINUE THROUGH THE FCST PD AS THE HIGH PRES RIDGE
PERSISTS OVER THE AREA.
AT KSAW...EXPECT VFR CONDITIONS TO PREVAIL THROUGH MUCH OF THE
PERIOD WITH HIGH PRES AND DRIER AIR PERSISTING OVER THE AREA. AS
WINDS BECOME NE OFF THE LAKE BY MIDDAY...COULD SEE AN MVFR STRATOCU
DECK REDEVELOP IN THE AFTERNOON AND THEN DISSIPATE TOWARD THE
EVENING AS LLVL FLOW VEERS MORE ELY.
&&
.MARINE (FOR THE 4 PM LAKE SUPERIOR FORECAST ISSUANCE)...
MAY SEE A FEW GALE FORCE GUSTS EARLY THIS EVENING OVER THE E HALF OF
LAKE SUPERIOR. OTHERWISE...EXPECT A DIMINISHING TREND...ESPECIALLY
LATE TONIGHT AS SFC HIGH PRES ARRIVES. HEAVY FREEZING SPRAY SHOULD
END TUE MORNING. NEXT ROUND OF STRONGER WINDS (20-30KT) WILL ARRIVE
THU INTO FRI AS ANOTHER ARCTIC AIRMASS DROPS INTO THE GREAT LAKES
REGION.
&&
.MQT WATCHES/WARNINGS/ADVISORIES...
UPPER MICHIGAN...NONE.
LAKE SUPERIOR...
HEAVY FREEZING SPRAY WARNING UNTIL 7 AM EST TUESDAY FOR LSZ266-
267.
HEAVY FREEZING SPRAY WARNING UNTIL 7 AM EST TUESDAY FOR LSZ162-
263-264.
LAKE MICHIGAN...NONE.
&&
$$
SHORT TERM...ROLFSON
LONG TERM...KF
AVIATION...VOSS
MARINE...ROLFSON
AREA FORECAST DISCUSSION
NWS GAYLORD MI
1150 PM EST MON MAR 3 2008
.AVIATION...LAKE CLOUDS WILL BE IN AND OUT OF THE TERMINAL SITES
INTO THE MORNING HOURS...PERHAPS A FEW FLURRIES OR LIGHT SNOW
SHOWERS ESPECIALLY AT TVC/PLN. EXPECT CLOUD COVER TO DECREASE
TUESDAY AFTERNOON.
&&
.PREV DISCUSSION... /ISSUED 1011 PM EST MON MAR 3 2008/
LAKE EFFECT SNOW SHOWERS THE MAIN ISSUE OVERNIGHT AS COLD AIR RETURNS
TO THE WESTERN GREAT LAKES. 02Z SURFACE ANALYSIS SHOWS COLD FRONT
THAT PASSED THROUGH THE FORECAST AREA THIS MORNING CROSSING THE
EASTERN LAKES...WITH A RIDGE OF HIGH PRESSURE IN ITS WAKE OVER THE
NORTHERN AND CENTRAL PLAINS BUILDING INTO THE STATE WHERE 3-4MB/3H
PRESSURE RISES EXIST. A SECONDARY COLD FRONT RUNS EAST-WEST ACROSS
FAR NORTHERN LAKE SUPERIOR. WATER VAPOR IMAGERY SHOWS A SHORT WAVE
TROUGH IN THE NORTHERN BRANCH OF A SPLIT FLOW PATTERN IN PLACE
OVER THE NATION`S MIDSECTION CROSS LAKE SUPERIOR/WESTERN WI/
EASTERN WI THIS EVENING. AS THIS FEATURE CROSSES THE LOWER
PENINSULA AND MID LEVEL WINDS VEER MORE WESTERLY OVERNIGHT...
MID/HIGH CLOUDS ASSOCIATED WITH EXTENSIVE FRONTAL PRECIPITATION
BAND WILL PUSH OUT OF LOWER MI...LEAVING BEHIND LAKE GENERATED SC.
SNOW SHOWER ACTIVITY SO FAR THIS EVENING HAS BEEN CONFINED TO
EASTERN UPPER MI WHERE LOW LEVEL TEMPERATURES ARE COLDER (AOB
-16C) AND INVERSIONS RUNNING AROUND 875MB PER AIRCRAFT SOUNDINGS.
SNOWFALL RATES HAVE BEEN PRETTY DECENT AT TIMES WITH OCCASIONAL
FORAYS DOWN TO ONE-HALF MILE VISIBILITY AT BOTH SOO MI AND
ONTARIO. COLD AIR CONTINUES TO ADVECT ACROSS LAKE SUPERIOR WITH
850MB TEMPERATURES EXPECTED TO DROP BELOW -20C. COMBINATION OF
COLD ADVECTION AND ASCENT ASSOCIATED WITH PASSING SHORT WAVE
TROUGH FORECAST TO NUDGE INVERSION HEIGHTS CLOSER TO THE 800MB
LEVEL. AT THE SAME TIME HOWEVER ATMOSPHERE CONTINUES TO DRY OUT
ABOVE INVERSION (850-700MB RH FALLING BELOW 30 PERCENT)...MAY
ALREADY BE SEEING THIS MANIFEST ITSELF WITH A MARKED DECREASE IN
CLOUD/PRECIP COVERAGE OVER PAST COUPLE OF HOURS. WINDS BEGINNING
TO VEER MORE NORTHWEST OVER NORTHERN LAKE SUPERIOR...SO EXPECT
WE`LL CONTINUE TO SEE MULTIPLE BAND CONVECTION INTO EASTERN UPPER
MUCH OF THE NIGHT BEFORE LOW LEVEL FLOW BREAKS DOWN AS GRADIENT
WEAKENS LATE. DID BUMP ACCUMULATIONS UP A BIT AROUND WHITEFISH
BAY. ACROSS NORTHERN LOWER...MOSTLY FLAT SC AND SOME FLURRIES
NORTH OF M-72 AS INSTABILITY PRETTY MARGINAL. WILL PROBABLY STAY
THAT WAY MOST OF THE NIGHT AS 850MB TEMPERATURES BARELY DROP TO
-15C OVER NORTHERN LAKE MICHIGAN. LOW LEVEL FLOW BECOMING MORE
NORTHWEST LATER TONIGHT OPENING UP A LONGER EFFECTIVE FETCH WHICH
SHOULD AUGMENT CURRENT CLOUD AND FLURRY/LIGHT SNOW SHOWER
DEVELOPMENT ESPECIALLY FROM GRAND TRAVERSE BAY NORTHWARD. BUT NOT
EXPECTING THIS TO GET TOO OUT OF HAND.
JPB
PREV DISCUSSION... /ISSUED 328 PM EST MON MAR 3 2008/
DEPARTING COLD FRONT NOW EXTENDS FROM JUST EAST OF JAMES BAY THRU
SE ONTARIO IN FAR SE LOWER MICHIGAN. UPPER TROUGH IS MOVING INTO
THE WRN GREAT LAKES REGION ATTM. CAA CONTINUES...BUT COLDEST AIR
IS STILL WELL WEST OF MICHIGAN ALONG AND WEST OF THE 500 MB TROUGH
AXIS. SYNOPTICALLY-DRIVEN SNOW HAS EXITED OUR CWA. LIGHT LAKE
EFFECT SNOW SHOWERS HAVE BEGUN TO DEVELOP ACROSS ERN UPR MICHIGAN
AS DELTA T`S RISE INTO THE TEENS. LAKE EFFECT SNOW SHOWERS HAVE
YET TO DEVELOP ACROSS NW LOWER MICHIGAN AS 850 MB TEMPS ARE STILL
TOO WARM TO PRODUCE SUFFICIENT OVER-LAKE INSTABILITY. WX WILL
REMAIN RELATIVELY QUIET BUT QUITE COLD OVER THE NEXT 24 HOURS AS
COLD CANADIAN HIGH PRESSURE BUILDS INTO THE UPPER MID WEST AND THE
GREAT LAKES. ATTENTION THEN TURNS AGAIN TO SNOW CHANCES AS A SRN
STREAM STORM SYSTEM LIFTING THRU THE ERN THIRD OF THE US TUESDAY
NIGHT AND WEDNESDAY.
TONIGHT AND TUESDAY...STRONG SURFACE RIDGING WILL BUILD INTO
MICHIGAN TONIGHT...WITH THE HIGH CENTER PASSING JUST NORTH OF THE
STATE ON TUESDAY. LAKE EFFECT SNOW PARAMETERS ARE MORE FAVORABLE
ACROSS UPPER MICHIGAN...WHERE DELTA T`S WILL BE IN THE UPPER TEENS
TO NEAR 20...900-700 MB RH WILL BE 50-60 PCT AND INVERSION HEIGHT
WILL BE 4-5 KFT. NMRS SNOW SHOWERS WILL CONTINUE TO IMPACT ERN UPR
MICHIGAN...TARGETING NRN CHIPPEWA COUNTY FOR GREATEST COVERAGE AND
HIGHEST AMOUNTS UNDER THE DIRECTION OF NW FLOW. HOWEVER...ONLY
EXPECT ANOTHER INCH OR TWO OF NEW SNOW ACCUMULATION GIVEN
STRENGTHENING SUBSIDENCE AND DRY AIR. LAKE EFFECT SNOW PARAMETERS
ARE QUITE MARGINAL ACROSS NRN LOWER MICHIGAN...FURTHER LIMITED BY
EXTENSIVE ICE COVERAGE ACROSS FAR NRN LAKE MICHIGAN. DELTA T`S
WILL RISE INTO THE LOW TO MID TEENS...900-700 MB RH WILL ONLY BE
AROUND 40 PCT...DROPPING TO AROUND 20 PCT BY 12Z TUESDAY AND
INVERSION HEIGHTS WILL DROP FROM AROUND 4 KFT THIS EVENING TO 2500
FEET BY DAYBREAK. WILL KEEP A CHANCE OF FLURRIES IN THE SNOWBELT
REGIONS OF NW AND N CENTRAL LOWER MICHIGAN TONIGHT. TUESDAY LOOKS
DRY ACROSS OUR ENTIRE CWA AS WINDS SHIFT TO THE NE AND DELTA T`S
DROP BELOW 10 C. A VERY COLD NIGHT IS IN STORE FOR THE
REGION...WITH LOW TEMPS PLUMMETING INTO THE SINGLE DIGITS. TEMPS
SHOULD REBOUND INTO THE 20S TO NEAR 30 TUESDAY AFTERNOON.
TUE NIGHT THRU THU...MAIN FCST FOCUS OBVIOUSLY ON SYSTEM TO AFFECT
THE OHIO VALLEY INTO TUE NIGHT...AND JUST HOW FAR NORTH ACCUMULATING
SNOWS WILL TAKE SHAPE. FRONT WHICH CROSSED THE REGION THIS MORNING
WILL LAY DOWN OVR THE NORTHERN OHIO VALLEY TONIGHT AS DRIVING
NORTHERN STREAM ENERGY SHEARS OUT INTO QUEBEC. FOCUS WILL THEN SHIFT
TO THE TAIL END OF THIS FRONT OVER THE LOWER MISS VALLEY
OVERNIGHT...AS SECONDARY PIECE OF ENERGY EMERGING FROM THE SOUTHERN
PLAINS AIDS IN CYCLOGENESIS ALONG THE BOUNDARY...WITH SFC CYCLONE
PROGGED TO STEADILY DEEPEN AS IT ADVANCES TOWARD THE LOWER OHIO
VALLEY TUE EVENING. MAJORITY OF MODEL GUIDANCE (EVEN THE 12Z UKMET
WHICH HAS BEEN STUBBORNLY WEST THUS FAR) HAS FINALLY NARROWED IN ON
A PRIMARY SOLUTION DRIVING THE SFC CYCLONE TOWARD WESTERN PA BY 00Z
WED AS THE UPPER ENERGY SHEARS OUT OVR THE OHIO VALLEY. THIS
SOLUTION HAS MERIT GIVEN OVERALL DEEPLY CONFLUENT FLOW IN THE
NORTHERN STREAM OVR THE NORTHERN GREAT LAKES/NORTHEAST...WHICH
SHOULD REINFORCE BLOCKING LOW LEVEL RIDGING ADVANCING THRU THIS
REGION...THEREBY KEEPING MUCH OF THE SYSTEM OFF TO THE SOUTH. THE
QUESTION IS STILL WITH THE FAR SOUTHEAST CWA...WHERE 12Z GUIDANCE
CONTINUES TO HINT AT NORTHERN FRINGES OF DEFORMATION-DRIVEN PRECIP
SHIELD MAKING INROADS. 12Z NAM/GFS AND GEFS ENSEMBLE MEAN SUPPORT
THIS SOLUTION...BUT GIVEN OVERALL NATURE OF PRIMARY FORCING RAPIDLY
SHEARING OUT...PREFER TO HOLD WITH ONLY CHANCE POPS AT THIS
JUNCTURE...AS EVEN IF IT DOES SNOW...SHOULD NOT BE MUCH
ACCUMULATION. OF COURSE...WILL HAVE TO WATCH FOR THE SEEMINGLY
ENDLESS NORTHWEST TREND...BUT OVERALL THIS ONE LOOKS LIKE A NEAR
MISS.
A BRIEF RESPITE STILL LOOKS ON TAP INTO WED AFTN BEFORE NEXT UPR
WAVE (COMING ASHORE OVR THE PAC NORTHWEST THIS AFTN) HEADS THRU THE
UPR MIDWEST...WITH ASSOCIATED SHOT OF WEAK 700-500MB -DIVQ
APPROACHING THE WESTERN CWA. MOISTURE WITH THIS SYSTEM APPEARS QUITE
LIMITED (OF PACIFIC ORIGIN)...BUT LIKELY ENOUGH TO SQUEEZE OUT A FEW
SNOW SHOWERS WED NIGHT AND ESPECIALLY INTO THU AS REINFORCING ENERGY
BEGINS TO CARVE OUT DEEPER TROUGHING OVR THE UPR MIDWEST (SEE BELOW
FOR MORE DETAILS). HIGHS THRU THE PERIOD LOOK TO REMAIN JUST A BIT
BELOW EARLY MARCH AVGS...OWING PRIMARILY TO CLOUD COVER...WITH
READINGS MAINLY UPR 20S/LOW 30S.
LATER PERIODS (THU NIGHT INTO MON)...SEMI-ACTIVE WX REGIME LOOKS TO
CONTINUE INTO AT LEAST A PORTION OF THE WEEKEND...AS THE OVERALL UPR
PATTERN REMAINS DOMINATED BY MEAN TROUGHING OVER THE CENTRAL/EASTERN
CONUS...A RESULT OF CONTINUED STRONG NORTH PACIFIC JET FORCING AND A
SUBSEQUENT MAINTENANCE OF MERIDIONAL MID LEVEL RIDGING OVER THE
EASTERN PACIFIC/WESTERN CONUS. MEDIUM RANGE GUIDANCE (INCLUDING THE
GFS ENSEMBLE MEAN) REMAINS IN GOOD AGREEMENT WITH REGARD TO YET
ANOTHER SHOT OF VERY COLD AIR (BY EARLY MARCH STANDARDS) BEING
SHUNTED INTO THE GREAT LAKES FRI/SAT TIME FRAME...AS DEEP TROUGHING
INTO THE GULF OF ALASKA AIDS IN FURTHER AMPLIFICATION OF THE WESTERN
RIDGE AND A DISLODGING OF THE POLAR VORTEX TOWARD SOUTHEAST
CANADA...RESULTING IN ARCTIC AIR ONCE AGAIN OVERTAKING THE REGION
HEADING INTO THE WEEKEND. END RESULT SHOULD BE ANOTHER ROUND OF SOME
LAKE EFFECT/LAKE ENHANCED SNOW SHOWERS GIVEN MORE THAN SUFFICIENT
INSTABILITY AND DEEP LAYER CYCLONIC FLOW IN PLACE...HOWEVER THIS
CERTAINLY APT TO CHANGE PENDING EVENTUAL AVAILABLE MOISTURE/LOCATION
OF THE MEAN UPPER TROUGH. THEREAFTER...GUIDANCE IN AGREEMENT ON A
GRADUAL FLATTENING OF THE WESTERN RIDGE AS PACIFIC ENERGY SPILLS
INLAND...WITH TROUGHING OVERHEAD BEING SHUNTED TO THE EAST AND
OVERALL LOW/MID LEVEL RIDGING TAKING HOLD TO ROUND OUT THE WEEKEND.
OF COURSE...THE DETAILS ARE APT TO CHANGE (LIKELY TOWARD A SLOWER
DEPARTURE OF THE COLD AIR)...BUT AT THIS POINT WILL CONTINUE THE DRY
FCST FOR SUN/MON TIME FRAME.
LAWRENCE
&&
.APX WATCHES/WARNINGS/ADVISORIES...
MI...NONE.
LM...NONE.
LH...SMALL CRAFT ADVISORY UNTIL 5 AM EST TUESDAY FOR LHZ347.
&&
$$
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