[MCD] SWOMCD

Sun Mar 19 02:02:21 UTC 2006

ACUS11 KWNS 190204
SWOMCD
SPC MCD 190204 
SDZ000-NEZ000-190600-

MESOSCALE DISCUSSION 0307
NWS STORM PREDICTION CENTER NORMAN OK
0804 PM CST SAT MAR 18 2006

AREAS AFFECTED...WRN SD/WRN AND CNTRL NEB

CONCERNING...PRECIPITATION TRENDS...WINTER PRECIPITATION 

VALID 190204Z - 190600Z

...WINTER PRECIPITATION WILL BEGIN AS A MIX OF FZRA/FZDZ ACROSS WRN
SD AND PORTIONS OF WRN AND CNTRL NEB BEFORE CHANGING TO SNOW LATER
TONIGHT...

LATEST WV IMAGERY SHOWS STRONG UPPER LOW MOVING INTO NRN AZ/SRN UT
THIS EVENING. INCREASING PVA AHEAD OF THE UPPER LOW WILL FOCUS A
BROAD AREA OF LARGE SCALE ASCENT ACROSS THE NRN HIGH PLAINS WHERE
HEAVY SNOW WILL DEVELOP LATER TONIGHT. MEANWHILE...MAINLY LIGHT SNOW
CONTINUES ACROSS PORTIONS OF ND AND ERN SD ALONG A WEAK DEFORMATION
BAND NEAR 700MB. 

WEST OF THIS ZONE...LIGHT FREEZING RAIN WAS FALLING. 00Z SOUNDING AT
RAPID CITY INDICATED A SATURATED SUB-FREEZING LAYER FROM THE SFC TO
AROUND 750MB...WITH A DRY LAYER ABOVE. TEMPERATURES IN THE LOW
LAYERS ARE NOT COLD ENOUGH /I.E. BELOW -10C/ FOR THE AIRMASS TO
CONTAIN ICE CRYSTALS NECESSARY FOR SNOW...SO A PERIOD OF FZRA/FZDZ
WILL CONTINUE UNTIL THE COLUMN COMPLETELY SATURATES AND COOLS
FURTHER.

STRONG LOW LEVEL WARM ADVECTION IS OCCURRING ACROSS THE ENTIRE AREA
AHEAD OF APPROACHING UPPER SYSTEM. A LARGE AREA OF LOW CLOUDS ACROSS
NEB/SD EARLIER IN THE DAY /PARTIALLY IN RESPONSE TO THE UPSLOPE
FLOW/ RESTRICTED DIURNAL HEATING...SO HIGH TEMPS WERE ONLY IN THE
LOW/MID 30S ACROSS SD/NEB...AND THIS WILL MAKE A DIFFERENCE WITH
REGARD TO RAIN OR FREEZING RAIN IN THE NEXT FEW HOURS. SFC WET BULB
TEMPS ARE IN THE MID 20S TO LOW 30S ACROSS WRN SD...SO MAIN PTYPE
WILL BE FZRA/FZDZ. AMOUNTS WILL NOT BE HEAVY...BUT FORECAST
SOUNDINGS SUGGEST FREEZING PCPN MAY PERSIST FOR 2-4 HOURS BEFORE
CHANGING TO SNOW. ACROSS WRN NEB...MAIN PTYPE WILL BE RAIN...EXCEPT
IN AREAS WHERE TEMPS FALL TO 32F OR BELOW. HEAVIER PCPN WILL BEGIN
IN EARNEST AFTER 05-06Z.

..TAYLOR.. 03/19/2006

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...FSD...ABR...LBF...UNR...CYS...

40980133 41110385 42850401 45880385 45900123 44049947
42309865 41159989 

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