Frost and Freeze in Delaware, April 5 to 11, 2007

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MOUNT HOLLY NJ
350 AM EDT THU APR 5 2007

.OVERVIEW...
AN UNSEASONABLY COLD RUN OF WEATHER IS UNDERWAY FOR OUR CWA WITH
TEMPS EXPECTED TO BE COLDER THAN NML THRUT THE CUR DETERMINISTIC
FCST PKG. CYCLOGEN STILL EXPECTED TO OCR ALG/NEAR THE MID ATLC COAST
FRI NGT WITH THE GREATEST PSBLTY FOR MSRBL PCPN (AND SNOW) IN OUR
DELMARVA ZONES. AFTER THIS LOW DEPARTS A RENEWED NW FLOW OF
UNSEASONABLY COLD WX WILL CONT BEFORE TEMPS MODERATE TWD THE MIDDLE
OF NEXT WEEK ALG WITH THE START OF WHAT LOOKS LIKE THREE SYNOPTIC
SCALE SHOTS AT PCPN. PRIOR TO THAT THE COLD POOL ALF WILL PRODUCE
SOME INSTAB SHOWERS THRU MON NGT. BOTH THE GFS AND WRF NMM INIT
PRETTY CLOSE. OTHER MED RNG MDLS ARE CLOSER TO THE GFS THAN THE WRF
WRT TO THE CYCLOGEN AND WE WILL LEAN TWD THE GFS SOLN AS IT NORMALLY
HAS BETTER SKILL THAN THE WRF-NMM AT THAT FORECAST TIME FRAME.

&&

.SHORT TERM /TODAY THROUGH FRIDAY/...
EVEN W/O THE SUN TO SELF DESTRUCT, THE SC IS DOING PRETTY GOOD AT
GETTING INTO OUR CWA. CHANNELIZED VORT MAX WILL SLOWLY LIFT NWD.
DEEPEST MSTR REMAINS IN THE NRN PART OF OUR CWA WHERE WE WILL CONT
OUR POPS. FTHR TO THE S, SOME SPRINKLES CANT BE RULED TOTALLY OUT,
BUT WE BELIEVE THERE IS A LESSER CHC THE FTHR S ONE IS WI OUR CWA.
WITH THE CONVECTIVE TEMPS BEING SO LOW, WE BELIEVE THE HIER MAX
TEMPS AS DISPLAYED BY THE STAT GUID WONT BE ABLE TO BE REACHED.
WE ARE LEANING TWD THE LOWER ETA MOS. LASTLY, WINDS ALF WILL BE
MIXED RATHER EASILY TDY, BUT WINDS ALF ARE NOT STRONG ENUF TO REACH
WIND ADVY CRIT. GUSTS IN THE 30S ARE LIKELY IN MOST PLACES.

CHANNELIZED VORT MAX CONTS TO LIFT NWD TNGT AND WILL BE ALG THE NRN
EDGE OF OUR CWA BY FRI MRNG. WITH THE LOSS OF THE SUN (DIRECT OR
INDIRECT) AND NO COLDER AIR MOVG IN ALF, THE SHOWERS SHLD DECREASE.
THE FCST GRAD LOOKS TOO TIGHT TO PERMIT RDTNL COOLING. SO SOME OF
THE SHELTERED AREA MOS MIN TEMPS WERE RAISED. NEVERTHELESS MOST/ALL
OF OUR CWA IS EXPECTED TO GO BLO FREEZING TNGT. IF NOT TONIGHT, SUB
FREEZING TEMPS ARE LKLY THROUGH SUNDAY NGT AND POSSIBLY EVEN MON
NGT. SUBFREEZING TEMPS ARE GOING TO DAMAGE COLD SENSITIVE PARTS OF
VEGETATION THAT HAS ALRDY SPROUTED. WHAT COMES TO MIND IS MY
NEIGHBORS LOVELY MAGNOLIA BLOSSOMS THAT WILL LOOK LIKE WET PAPER
BAGS. ON A MORE SERIOUS AND AGRICULTURAL NOTE, IT APPEARS THAT MOST
FRUIT TREES ARE PBLY NOT FAR ENOUGH ALONG TO BE DAMAGED WITH THE
POSSIBLE EXCEPTION OF PEACHES. WE ARE FORTUNATE THAT THIS DID NOT
OCCUR A WEEK OR TWO LATER. FOR NOW, WE WILL HOLD OFF ON ANY FREEZE
WRNGS BASED ON OUR TARGET STARTING DATE OF 4/15. IN REALITY BASED ON
THE PROGRESSION OF PEACH BLOSSOMS, LOOKS LIKE ITS MORE OF A HARD
FREEZE (TEMPS LESS THAN 28F) WARNING THAT WOULD BE NEEDED. WE WILL
CONT WORDING IN THE HWO. PLEASE CHECK FOR POSSIBLE UPDATES LATER
TODAY. WE/LL CHECK WITH STATE AG CENTERS TO SEE IF THE FRUIT TREES
HAVE MADE GREATER PROGRESSION THAN WE CUR BELIEVE.

RECORD MIN TEMPS FOR TNGT (THE EVENT THAT YEAR SHOULD RING A BELL)
ATLANTIC CITY 24 IN 1982
PHILADELPHIA  24 IN 1982
WILIMINGTON   24 IN 1982
ALLENTOWN     18 IN 1982
TRENTON       21 IN 1898
GEORGETOWN    28 IN 1970
READING       20 IN 1982
MOUNT POCONO   5 IN 1914

ON FRIDAY LOOKS LIKE WE WILL BE IN A PVA LULL, BUT WITH STILL A
CYCLONIC FLOW ALOFT. CONVECTIVE TEMP STILL SHLD BE REACHED AND  WE
EXPECT PLENTY OF CLOUDS TO REFORM AGAIN. WE WILL LIMIT THE MNTN OF
PCPN TO JUST OUR FAR NRN ZONES ATTM WHERE MSTR REMAINS DEEPER. THERE
IS ALSO A SLIGHT RELAXATION TO THE CHILLY AIR MASS.  WE WILL BUMP UP
MAX TEMPS SLGTLY FROM TDY. WE STILL BELIEVE THE HIER MOS DATSETS
WON/T WORK BECAUSE OF THE LOW CONVECTIVE TEMPS.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
THERE IS BETTER MDL CONSISTENCY WITH THE NEXT SYSTEM COME FRIDAY
NIGHT. OTHER THAN THE WRF-NMM WHICH SOMETIMES HAS PBLMS LATCHING
ONTO LOWS THIS FAR IN THE FUTURE, THE OTHER MED RNG MDLS ALL HAVE A
PCPN EVENT ACRS THE SERN PART OF OUR CWA. THE GFS TAKES IT A STEP
FURTHER WITH WHAT APPEARS LIKE A CONVECTIVE FEEDBACK BULLSEYE. AS
THE SHORT WAVE SHARPENS WHAT WILL OR WILL NOT OCCUR IS CONVECTIVE IN
NATURE AS WE CAN FOLLOW THE TT BULLSEYE CURRENTLY OVER ALBERTA.
WOULD HAVE LIKED TO HAVE SEEN MORE MDL CONSISTENCY BY NOW WRT QPF,
BUT NEVERTHELESS ALL THE MDLS ARE FOCUSING A DECENT DPVA SHOT ACRS
THE SRN PART OF OUR CWA. WE WILL INCREASE POPS. TEMPS INIT IF PCPN
COMES IN FAST ENUF (SE CWA) WOULD START AS RAIN. THIS IS ALSO
SUPPORTED BY THE THERMAL FEATS AND LLVL THICK FCST. EVENTUALLY THO
AIR MASS EVAP/DYNAMICALLY COOLS TO SNOW EVEN WELL SE. ELSW THERE ARE
WEKAER SHRT WVS PROGGED TO MOVE THRU AND WE WILL CONT THE LWR CHC.
WE WILL THEN END THE SYNOPTIC SCALE PCPN CHCS ON SAT MRNG.

REST OF EXTDD LEFT AS IS: FOR THE MOST PART, MOST AREAS WILL HAVE
DRY WEATHER IN THE EXTENDED PERIOD. THE SOUTHERN POCONOS AND
NORTHERN NJ WILL HAVE CHC FOR DAYTIME RAIN AND NIGHTTIME SNOW
SHOWERS THIS WEEKEND AND MONDAY. CHC POPS WERE PLACED IN THE WED
PERIOD FOR MOST AREAS AS WARM AIR ADVECTION AND AN APPROACHING
DISTURBANCE FROM THE PLAINS ARRIVE ON THE SCENE.

&&

.AVIATION...
FOLLOWING YESTERDAYS FRONTAL PASSAGE, WEST TO NW WINDS USHERED IN
COOLER DRIER AIR. SKIES CLEARED FOR A BRIEF PERIOD OVERNIGHT BUT
SC IS ALREADY MOVING BACK INTO THE FORECAST AREA. EXPECT BKN TO OVC
SC N AND W WITH A FEW RAIN OR SNOW SHOWERS EXTREME NW. FARTHER S AND
E SC WILL BE BKN TO OCCASIONALLY SCT. VSBYS WILL BE UNRESTRICTED
EXCEPT BRIEFLY LOWER IN ANY SHOWERS. THESE CONDITIONS WILL
CONTINUE INTO TONIGHT.

&&

.MARINE...
WINDS HAVE SWUNG AROUND TO WNW AND ARE GUSTING TO OVER 25 KT.
WAVES ARE RUNNING 5 TO 7 FT ON THE OCEAN AND 2 TO 4 FT ON DELAWARE
BAY. THE STRONG W TO NW FLOW WILL CONTINUE TODAY INTO TONIGHT, THEN
DIMINISH LATER TONIGHT INTO FRIDAY. SMALL CRAFT ADVISORIES WILL
REMAIN UP UNTIL FRIDAY MORNING. LOW PRESSURE IS THEN EXPECTED
TO DEVELOP ALONG THE MID ATLANTIC COAST FRIDAY NIGHT AS AN
UPPER LEVEL LOW DROPS DOWN FROM THE GREAT LAKES. THE LOW WILL
INTENSIFY SATURDAY AS IT MOVES NE AWAY FROM THE EAST COAST.
THIS WILL ALLOW WINDS AND SEAS TO APPROACH SMALL CRAFT ADVISORY
CRITERIA.

&&

.PHI WATCHES/WARNINGS/ADVISORIES...
PA...NONE.
NJ...NONE.
DE...NONE.
MD...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT FRIDAY FOR ANZ430-431-
     450>455.

&&

OVERVIEW/SHORT TERM...GIGI
LONG TERM...OGIGI & HARA
AVIATION/MARINE...RPW

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