797
FOUS11 KWBC 061750
QPFHSD
PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
150 PM EDT MON APR 6 2026
VALID 12Z MON APR 06 2026 - 12Z THU APR 09 2026
..MISSOURI VALLEY/CORN BELT
DAY 1...
THE GUIDANCE CONTINUES TO SUGGEST THAT A HYPER-LOCALIZED BY INTENSE
BAND OF SNOWFALL WILL DEVELOP FROM EASTERN NE THROUGH SOUTHERN IA
AND POTENTIALLY AS FAR AS NORTHERN MO TONIGHT AND PERSIST INTO LATE
TUESDAY MORNING. SNOWFALL RATES WITHIN THIS BAND WILL LIKELY
ECLIPSE 1"/HR AT TIMES (80% CHANCE FROM THE WPC PROTOTYPE SNOWBAND
TOOL), AND AS THIS BAND TRANSLATES SLOWLY E/NE. THIS WILL CREATE
SIGNIFICANT SNOW ACCUMULATIONS, BUT WITH A VERY NARROW FOOTPRINT,
AND DIFFICULT COMMUTING TUESDAY MORNING.
THIS BAND IS EXPECTED TO DEVELOP AS A WEAK SHORTWAVE EMERGES FROM
THE CENTRAL ROCKIES AND ADVECTS E/SE CREATING SUBTLE HEIGHT FALLS
AND MID-LEVEL DIVERGENCE ACROSS THE AREA. AT THE SAME TIME, A
POTENT JET STREAK AROUND 130KTS WILL PIVOT EASTWARD OVER THE UPPER
MIDWEST, LEAVING ITS DISTANT RRQ OVER THE CORN BELT. THE OVERLAP OF
THE BEST DIVERGENCE AND UPPER DIFFLUENCE WILL OCCUR OVER NE/IA,
COINCIDENT WITH THE PLACEMENT OF STRONGEST 850MB WARM/MOIST
ADVECTION AS SOUTHERLY RETURN FLOW EMERGES FROM THE GULF. THE
CONCURRENT SURGE OF THE ACCOMPANYING THETA-E RIDGE WILL DRIVE
SUFFICIENT MOISTURE NORTHWARD, AND ALTHOUGH PWS ARE EXPECTED TO BE
NEAR NORMAL, THERE IS A NARROW CORRIDOR OF SPECIFIC HUMIDITY IN THE
700-500MB LAYER WHICH IS PROGGED TO EXCEED THE 90TH PERCENTILE
ACCORDING TO NAEFS. THIS IS A PERFECT OVERLAP WITH THE STRONGEST
FGEN (WITHIN THE 700-500MB LAYER) SUGGESTING THAT A NARROW BAND OF
HEAVY PRECIPITATION IS LIKELY, WITH SNOW LIKELY THE PRIMARY P-TYPE
AS ASCENT CROSSES THE DEEPENING DGZ.
SURFACE TEMPERATURES WILL BE AROUND TO SLIGHTLY ABOVE 0C, BUT THE
REST OF THE COLUMN WILL BE SUB-FREEZING SO AS SOON AS INTENSITY
RAMPS UP (WHICH WILL BE QUICKLY TONIGHT) PRECIPITATION WILL CHANGE
TO HEAVY SNOW, WITH THE AFOREMENTIONED 1"/HR+ RATES BECOMING
DOMINANT WITHIN THIS NARROW PLUME. AS THE BAND PIVOTS SLOWLY
NORTHEAST, IT WILL LEAD TO RAPID ACCUMULATIONS, AND THE HIGH-RES
GUIDANCE IS BEGINNING TO FOCUS FROM EASTERN NE THROUGH SW IA AS THE
AREA OF MOST INTENSE SNOWFALL, AND MANY OF THE DETERMINISTIC MODELS
SUGGEST 6+ INCHES OF SNOW, WHICH IS ALIGNED WITH THE NBMV5.0 PMM.
SINCE MOST OF THIS SNOW WILL OCCUR OVERNIGHT INTO THE MORNING
HOURS, MELTING LOSS DUE TO THE SUN IS NOT EXPECTED TO BE AN ISSUE,
SO WHILE CONFIDENCE IN A NARROW BAND OF HEAVY SNOW WITH CONTINUOUS
AMOUNTS OVER 6" REMAINS MODEST, THE THREAT FOR SIGNIFICANT IMPACTS
HAS INCREASED, LEADING TO A HAZARDOUS MORNING COMMUTE. WPC
PROBABILITIES HAVE CLIMBED DRAMATICALLY WITH THE INCREASE IN THE
12Z GUIDANCE SUITE, AND NOW REFLECT A 50-70% FOR AT LEAST 4 INCHES
FROM NEAR OMAHA, NE THROUGH SOUTH-CENTRAL IA. LOCALLY 6-10" OF SNOW
IS POSSIBLE IF THIS BAND CAN LINGER IN ANY ONE AREA WITH THE 1+"/HR
SNOWFALL RATES.
..GREAT LAKES & NORTHEAST
DAYS 1-2...
STRUNG OUT VORTICITY ASSOCIATED WITH A COMPACT SHORTWAVE WILL SWING
FROM THE GREAT LAKES TO THE NORTHEAST TONIGHT AND TUESDAY. THE
MODEST HEIGHT FALLS AND PVA WILL LEAD TO A COMPACT LOW PRESSURE
DEVELOPING ALONG AN INVERTED TROUGH, AND AS THIS FEATURE MOVES EAST
D2 IT WILL BRING PERIODS OF MODERATE TO HEAVY SNOWFALL. THIS EVENT
WILL CONTAIN TWO PRIMARY MECHANISMS FOR HEAVY SNOW.
THE FIRST WILL BE ALONG THE INVERTED TROUGH IMMEDIATELY AHEAD OF
THE WAVE OF LOW PRESSURE. IN THIS AREA, THE TOTAL SNOWFALL IS
EXPECTED TO BE MINIMAL, BUT PERIODS OF CONVECTIVE SNOW SHOWERS ARE
EXPECTED AS LOW-LEVEL CONVERGENCE DRIVES ASCENT INTO AN AIRMASS
WITH MODEST INSTABILITY (SBCAPE 200-300 J/KG). WITH POCKETS OF
LOW-LEVEL FGEN ADDITIONALLY DRIVING ASCENT, SOME AREAS, ESPECIALLY
ACROSS UPSTATE NY AND CENTRAL/SOUTHERN NEW ENGLAND COULD RECEIVE
MULTIPLE ROUNDS OF SNOW SHOWERS WITH BRIEFLY HEAVY SNOW RATES,
GUSTY WINDS, AND PERIODIC VISIBILITY RESTRICTIONS.
THE MORE SUBSTANTIAL SNOWFALL ACCUMULATIONS ARE EXPECTED BEHIND THE
WAVE OF LOW PRESSURE AS CAA DEVELOPS TO PRODUCE LOW-LEVEL FGEN, AND
NW FLOW DRIVES SUBSTANTIAL UPSLOPE ENHANCEMENT INTO THE ADIRONDACKS
AND GREENS. THE COVERAGE AND INTENSITY OF THIS SNOWFALL IS AGAIN
EXPECTED TO BE MODEST, BUT WHERE UPSLOPE FLOW IS MOST PRONOUNCED,
WPC PROBABILITIES SUGGEST A 10-30% CHANCE OF 4+ INCHES OF SNOW,
ESPECIALLY ACROSS THE ADIRONDACKS/GREENS/WHITES. DEVELOPING
DEFORMATION, ALTHOUGH MODEST, OVERLAPPING THIS CAA COULD CAUSE THIS
SWATH OF SNOWFALL TO PROGRESS ALL THE WAY TO THE ATLANTIC COAST OF
MASSACHUSETTS WITH A CORRIDOR OF HEAVY SNOW RATES REACHING THE
PORTLAND/BOSTON AREA TUESDAY NIGHT, ALBEIT WITH MINIMAL
ACCUMULATIONS.
WEISS
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