Area Forecast Discussion
Issued by NWS Green Bay, WI

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FXUS63 KGRB 020815
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
315 AM CDT MON MAY 2 2016

FORECAST DISCUSSION FOR ROUTINE MORNING FORECAST ISSUANCE

.SHORT TERM...TODAY...TONIGHT...AND TUESDAY
ISSUED AT 314 AM CDT MON MAY 2 2016

SKIES WILL START OUT SUNNY THIS MORNING BUT SOME CONVECTIVE CLOUDS
ARE LIKELY THIS AFTERNOON AS A WEAK UPPER TROUGH COMES THROUGH. A
BRIEF SHOWER IS NOT OUT OF THE QUESTION BUT THINK VIRGA IS MORE
LIKELY WITH VERY DRY AIR IN THE LOW LEVELS. HIGHS TODAY SHOULD BE
AROUND NORMAL.

WEAK UPPER RIDGING TONIGHT SHOULD ALLOW FOR CLEAR SKIES AND
SEASONABLE TEMPERATURES.

AN APPROACHING COLD FRONT AND ASSOCIATED UPPER TROUGH WILL BRING
SHOWERS AND THUNDERSTORMS TO THE AREA TUESDAY AFTERNOON. DRY AIR
WILL MAKE FOR LITTLE INSTABILITY BUT WET BULB ZERO HEIGHTS OF 5000
TO 6000 FT MAY ALLOW FOR SHOWERS OR STORMS TO PRODUCE SMALL HAIL.
WOULD NOT BE SURPRISED IF SOME PLACES HAVE HAIL COVERING THE
GROUND. SEVERE STORMS NOT EXPECTED THOUGH. WARM ADVECTION AHEAD
OF THE FRONT SHOULD BRING TEMPERATURES AT LEAST FIVE DEGREES ABOVE
NORMAL.

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY
ISSUED AT 314 AM CDT MON MAY 2 2016

MODELS CONTINUE TO SHOW A HIGHLY-AMPLIFIED/BLOCKY PATTERN
DEVELOPING OVER THE CONUS BY MID-WEEK WITH ONE UPPER LOW CLOSING
OFF OVER CA AND ANOTHER CLOSED UPPER LOW OVER THE MID-ATLANTIC
STATES BY LATE WEEK. AN UPPER RIDGE TO RESIDE OVER THE CENTRAL
CONUS THROUGH FRIDAY...BUT IS EXPECTED TO WEAKEN NEXT WEEKEND IN
RESPONSE TO A SHORTWAVE TROUGH PUSHING ACROSS SOUTHERN CANADA/
NORTHERN TIER OF STATES. PRECIPITATION CHANCES APPEAR TO BE TIED
TO THE PASSAGE OF TWO COLD FRONTS (TUE/TUE NIGHT AND SATURDAY).
TEMPERATURES ARE EXPECTED TO HAVE QUITE A RANGE WITH WARMING TO
ABOVE NORMAL VALUES AHEAD OF EACH COLD FRONT...THEN FALLING BELOW
NORMAL BEHIND THE FRONTAL PASSAGE.

SHOWERS/ISOLATED THUNDERSTORMS WILL CONTINUE TO PUSH SOUTH ACROSS
NE WI TUESDAY EVENING AS THE COLD FRONT EXITS THE AREA. DESPITE
STRONG BULK SHEAR VALUES CARRYING OVER INTO THE EVENING...WANING
INSTABILITY WOULD PREVENT ANY STORMS FROM TURNING SEVERE. THE COLD
FRONT WILL BE WELL TO OUR SOUTH AFTER MIDNIGHT...HOWEVER CANNOT
RULE OUT A FEW LINGERING SHOWERS AS AN UPPER TROUGH DIGS SE OVER
THE GREAT LAKES AND BRING A CYCLONIC FLOW TO THE FORECAST AREA.
ONSET OF CAA...COUPLED WITH N-NW WINDS COULD EVEN PRODUCE A LITTLE
LAKE ENHANCEMENTOVER NORTH-CENTRAL WI. MIN TEMPERATURES TO RANGE
FROM THE MID TO UPPER 30S NORTH...MAINLY LOWER 40S SOUTH.

AS THIS UPPER TROUGH CONTINUES TO DIG SE FROM THE GREAT LAKES
TOWARD THE OHIO RIVER VALLEY ON WEDNESDAY...MODELS INDICATE THAT
AN UPPER LOW MAY FORM OVER LOWER MI WITHIN THIS TROUGH. THIS WOULD
KEEP A CYCLONIC FLOW OVER WI (ESPECIALLY EASTERN SECTIONS) AND
WITH A COLD POOL ALOFT...THIS COULD BRING A SLIGHT CHANCE OF RAIN
SHOWERS TO MUCH OF THE AREA. WEDNESDAY WILL ALSO BE A BLUSTERY AND
COOLER DAY WITH NORTH WINDS AT 10 TO 20 MPH AND GUSTS POSSIBLY
APPROACHING 30 MPH. MAX TEMPERATURES TO ONLY REACH THE UPPER 40S
TO LOWER 50S FAR NORTH...UPPER 50S FOR PARTS OF CENTRAL WI.

THE NEWLY FORMED CLOSED UPPER LOW/STRENGTHENING UPPER TROUGH ARE
EXPECTED TO MOVE INTO THE APPALACHIANS WEDNESDAY NIGHT WITH THE
CYCLONIC FLOW WEAKENING OVER WI. A RIDGE OF HIGH PRESSURE IS THEN
FORECAST TO MOVE INTO THE WESTERN GREAT LAKES DURING THE OVERNIGHT
HOURS AND ALLOW SKIES TO CLEAR AND WINDS TO DIMINISH. THIS
SCENARIO WILL BRING A COOL NIGHT TO THE AREA WITH MIN TEMPERATURES
IN THE LOWER TO MIDDLE 30S NORTH...MID TO UPPER 30S SOUTH. WE WILL
HAVE TO WATCH THE WIND SPEEDS CLOSELY AS ANY SIGNIFICANT DROP
(BELOW 5 MPH) COULD ALLOW PATCHY FROST TO FORM. SOME OF THE MODELS
ARE HINTING AT A WEAK SHORTWAVE TO DROP SE THROUGH THE NW FLOW
ALOFT ON THURSDAY...HOWEVER WITH THE SURFACE RIDGE NEARLY
OVERHEAD...DO NOT SEE ANYTHING MORE THAN PASSING CLOUDS WITH THIS
SHORTWAVE. OTHERWISE...MODIFYING TEMPERATURES ALOFT SHOULD ALLOW
MAX TEMPERATURES TO GET A LITTLE CLOSER TO NORMAL WITH READINGS
AWAY FROM LAKE MI REACHING THE LOWER TO MIDDLE 60S.

THIS SURFACE RIDGE AXIS SHOULD KEEP NE WI DRY THROUGH FRIDAY AS
THE HIGHLY-AMPLIFIED MEAN FLOW SETS UP A BLOCKING PATTERN ACROSS
THE CONUS. THE ONLY FLY IN THE OINTMENT COULD BE SOME CLOUDS
ACROSS THE NORTH AS A COLD FRONT TO SLOWLY SAG TOWARD LAKE
SUPERIOR. FRIDAY COULD BE A RATHER MILD DAY WITH MAX TEMPERATURES
RANGING FROM THE LOWER 60S NEAR LAKE MI...TO THE LOWER TO MIDDLE
70S OVER PARTS OF CENTRAL WI.

THE COLD FRONT IS PROGGED TO SLOWLY DROP SE INTO THE WESTERN GREAT
LAKES REGION LATE FRIDAY NIGHT INTO SATURDAY AND BRING THE NEXT
CHANCE FOR SHOWERS/THUNDERSTORMS TO NE WI. TOO EARLY YET TO
DETERMINE THE STRENGTH OF THESE STORMS...BUT IF WE CAN DESTABILIZE
ENOUGH AHEAD OF THE FRONT AND THERE IS ENOUGH MOISTURE IN PLACE...
THERE IS A POSSIBILITY OF AT LEAST STRONGER STORMS ON SATURDAY. IT
ALSO APPEARS THAT SATURDAY WILL BE ANOTHER MILD DAY WITH MAX
TEMPERATURES IN THE MID 60S NEAR LAKE MI...TO THE LOWER TO MIDDLE
70S ELSEWHERE.

CHANCES FOR SHOWERS/THUNDERSTORMS TO CONTINUE INTO SATURDAY NIGHT
AS THE COLD FRONT BEGINS TO PULL AWAY FROM THE REGION. A WEAK AREA
OF HIGH PRESSURE IS FORECAST TO MOVE INTO THE GREAT LAKES NEXT
SUNDAY AND ALLOW FOR DRYING TO OCCUR. A SLIGHTLY COOLER AIR MASS
TO ALSO SETTLE OVER THE REGION...THUS MAX TEMPERATURES ON SUNDAY
SHOULD BE IN THE MID TO UPPER 60S (COOLER LAKESIDE).
&&

.AVIATION...FOR 06Z TAF ISSUANCE
ISSUED AT 1119 PM CDT SUN MAY 1 2016

SURFACE HIGH PRESSURE RIDGE BUILDING INTO THE WESTERN GREAT LAKES
OVERNIGHT INTO MONDAY WILL PRODUCE VFR CONDITIONS. WEAK UPPER LOW
PRESSURE ALOFT THROUGH MONDAY...ALONG WITH STEEP LAPSE RATES DUE
TO COLD H7 TEMPERATURES WILL PRODUCE SCT-BKN MID LEVEL CLOUDS.
BOUNDARY LAYER DRY BUT VIRGA POSSIBLE MONDAY AFTERNOON.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$

SHORT TERM.....RDM
LONG TERM......KALLAS
AVIATION.......TDH



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