Sunday, January 13, 2019

3 comments:
How Much Longer & What About Monday?
UPDATE AS OF 10:45 AM ET SUN 1/13

  • NORTH OF THE PA LINE, LIGHT TO MODERATE SNOW CONTINUES THROUGH 7 PM BEFORE TAPERING TOWARD MIDNIGHT, WITH AN ADDITIONAL 2" 
  • FOR NORTHERN MD COUNTIES TO I-70/BALTIMORE CITY LINEMODERATE SNOW CONTINUES THROUGH 5 PM, THEN BECOMING LIGHTER AT TIMES AFTER SUNDOWN, WITH AN ADDITIONAL 4-5" AND STORM TOTALS OF 5-10" LIKELY.
  • FROM BALTIMORE CITY SOUTH TO DC METRO INCL. MONTGOMERY, ANNE ARUNDEL, PRINCE GEORGES, MODERATE SNOW TO CONTINUE THROUGH 10 AM, THEN BECOME HEAVY THROUGH 4 PM, WITH AN ADDITIONAL 4-6" PROBABLE IN MOST LOCATIONS, WITH 10" OR MORE LIKELY. TAPERING TO LIGHT SNOW AFTER 10 PM.
  • FOR THE EASTERN SHORE, HEAVY SNOW WILL CONTINUE AT A STEADY PAVE THROUGH NIGHTFALL, WITH WIDESPREAD 4-8" TOTALS FOR ALL AREAS NORTH OF OCEAN CITY. AREAS NEAREST THE BAY MAY EXCEED 8" BY 6 PM TODAY, WITH ACCUMULATING SNOW ENDING BY MIDNIGHT.
  • FOR ALL AREAS: SOME DECREASE TO LIGHT AND MODERATE SNOW INTENSITY EXPECTED FROM AROUND 6 PM, WITH SNOW STARTING TO EXIT THE REGION AROUND 10 PM. ACCUMULATING SNOW SHOULD END BY 12 AM, AND WITH TEMPERATURES REMAINING BELOW 32 MOST OF THE DAY, REFREEZING WILL QUICKLY DEVELOP BY SUNDOWN WITH LOWS IN MID 20S REGION-WIDE. 
  • ABOUT MONDAY: hWell, considering that Winter Storm Warnings were just extended to 12 AM Monday for most locations-- we think tomorrow is largely done for most schools and colleges. The NWS hourly chart above is from Parkville, MD a representative location for the region to illustrate that scattered light snow is still possible in some areas until at least 11 PM tonight. An upper level disturbance is expected to pass through in the final hours, and this would briefly enhance any last snow showers to produce up to 1/2" extra in the 8-11 PM period. This indicates icy conditions should be expected for the AM commute beyond major highways & beltways, specifically in backstreet roads, secondaries, bridges, overpasses and off ramps.
  • PLOWS & LOTS: Many plow operators may need to make three full passes for removal due to the extended duration of this event. If a late stage accumulation occurs, they would have to come back for a 4th pass. Crews working on school & bus lots will have to decide if there is adequate time to make one full cleanup once snow ends this evening, or should they start early knowing a second full pass will be needed before Monday morning?
  • SHORT RANGE SIMULATED RADAR: Snow exiting the 95 corridor around 11 PM as shown below in the High Resolution Rapid Refresh (HRRR) model.

Saturday, January 12, 2019

IF IT'S MEANT TO BE, IT'LL BE

15 comments:
A Weekend of "White in the Winter Night" 

7:15 PM ET SAT 1/12 UPDATE








  • WINTER STORM WARNINGS RAISED FOR MOST OF BALTIMORE-WASHINGTON METRO AREA FROM SATURDAY LATE AFTERNOON THROUGH 6PM SUNDAY FOR 4-8" OR MORE OF SNOW. 
  • DC METRO AND NORTHERN VIRGINIA MAY EXCEED 8" IN AREAS WHERE HEAVIEST SNOW OCCURS EARLY SUNDAY MORNING.
  • SHORT RANGE MODELS SHOW INCREASING POTENTIAL FOR A LATE SUNDAY PM SNOW SQUALL TO CROSS THE I-66 CORRIDOR AREA, PRODUCING AN ADDITIONAL 1/2-1"
  • BESIDES, if you're a Powderhound, isn't this is what we live for, right? Expecting snow and then finding out that your area has been UPGRADED to a WARNING! Golden.
  • SPECIAL NOTE ABOUT THE FORMER INSIDER APP: The Insider App program, operational during the 2015-2017 period is unfortunately no longer available. We do not yet have a projection on if or when this will resume, but are grateful for the generous support and readership many of you devoted to app in those years.
SNOWFALL TIMING & AMOUNTS

  • SATURDAY: Light snow developing in DC metro area/northern VA between 2-3 PM, in Baltimore metro from 3-4 PM, northern MD/PA line by 5 PM. Intensity will pickup into the evening as the eastward moving energy is transferred to a developing coastal low off North Carolina.
  • SATURDAY PM  - SUNDAY AM : Snow intensity region-wide for all areas will increase toward nightfall and continue overnight. This includes a region from the DC I-66 corridor north to the PA I-76 turnpike and east to the Chesapeake Bay & the Eastern shore of MD/DE. Up to 3" is probable by daybreak Sunday for these areas. Sunday AM activities including worship services likely to be impacted. Areas south of I-70 may receive 4" or more where heavier bands develop.
  • SUNDAY PM - MONDAY AM : Snow begins tapering south to north, ending in DC metro by Sunday noon, Baltimore metro region in mid afternoon,and southern PA/Eastern shore by sundown. With sub 30 F temperatures overnight Sunday and powdery snow composition refreezing on untreated surfaces, it is likely that travel delays and some disruptions will occur for the Monday AM commute. For schools, if a second round of snow occurs after grounds crews have cleared lots and prepared buses, Monday may be a challenging situation depending on one's location.
  • LET'S SEE WHERE THIS THING GOES... Short range computer models guidance continues to indicate that higher totals are possible, due either to moisture enhancement from the eventual coastal system, higher snowfall ratios due to cold air, or a northern creep of higher moisture levels. Any of these would result in surprise increases of 1-2" in snowfall totals in the final 6 hours of this event.

EARLIER MAPS & UPDATES BELOW

  • REPRESENTATIVE COMPUTER MODEL GUIDANCE FOR SNOWFALL SAT PM - SUN

Friday, December 7, 2018

TOO MUCH, TOO SOON

2 comments:
Too much, too soon.

5:30 AM ET FRI 12/7/18
  • HIGH PRESSURE RIDGE OVER THE NORTHERN STATES THIS WEEKEND WILL COUNTERBALANCE APPROACH OF A SOUTHERN WINTER STORM, KEEPING MAJORITY OF WINTRY PRECIP SOUTH OF THE D.C./I-66 CORRIDOR.
  • UP TO 6-12" POSSIBLE FROM SOUTHERN VIRGINIA TO CENTRAL & WESTERN  NORTH CAROLINA. Some areas will receive twice their normal seasonal snowfall in one event.  System may be an indicator of what a favorable pattern would able to produce in the Mid-Atlantic later in the season. 
  • FLURRIES OR OCCASIONAL LIGHT SNOW POSSIBLE in the DC metro area, with accumulating snow of 1-2" possible south of DC toward central Virginia. Baltimore metro area and north to PA unlikely to receive accumulation, but may see a passing snow shower at times on Sunday.

LATEST SURFACE MAP PROJECTION DEPICTS DUAL HIGH PRESSURE SYSTEMS KEEPING WINTER STORM LARGELY SOUTH OF MID-ATLANTIC, WITH HIGH IMPACT SNOWFALL CENTERED IN THE CAROLINAS.  See our previous report for probabilities. In short, it's too much cold air too soon for the Mid-Atlantic, and too much snow too soon for Carolinas.