May 25, 2017 1630 UTC Day 1 Convective Outlook
Updated: Thu May 25 16:19:35 UTC 2017 (20170525 1630Z Day 1 shapefile | 20170525 1630Z Day 1 KML)
Probabilistic to Categorical Outlook Conversion Table
Categorical Graphic
20170525 1630 UTC Day 1 Outlook Graphic
Day 1 Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
SLIGHT 32,314 175,343 Sterling, CO...Fort Morgan, CO...
MARGINAL 173,742 38,340,180 Philadelphia, PA...Baltimore, MD...Denver, CO...Washington, DC...Virginia Beach, VA...
Probabilistic Tornado Graphic
20170525 1630 UTC Day 1 Tornado Probabilities Graphic
Probability of a tornado within 25 miles of a point.
Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
2 % 27,827 17,835,802 Baltimore, MD...Washington, DC...Miami, FL...Hialeah, FL...Arlington, VA...
Probabilistic Damaging Wind Graphic
20170525 1630 UTC Day 1 Damaging Wind Probabilities Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point.
Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 13,036 62,912 No Major Population Center in Risk Area
5 % 171,206 36,969,021 Philadelphia, PA...Baltimore, MD...Denver, CO...Washington, DC...Virginia Beach, VA...
Probabilistic Large Hail Graphic
20170525 1630 UTC Day 1 Large Hail Probabilities Graphic
Probability of hail 1" or larger within 25 miles of a point.
Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk Area (sq. mi.) Area Pop. Some Larger Population Centers in Risk Area
15 % 32,258 175,101 Sterling, CO...Fort Morgan, CO...
5 % 167,555 32,483,203 Philadelphia, PA...Baltimore, MD...Denver, CO...Washington, DC...Virginia Beach, VA...
   SPC AC 251619

   Day 1 Convective Outlook  
   NWS Storm Prediction Center Norman OK
   1119 AM CDT Thu May 25 2017

   Valid 251630Z - 261200Z

   ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS
   AFTERNOON AND EVENING ACROSS PARTS OF NORTHEASTERN COLORADO AND
   SOUTHWESTERN NEBRASKA INTO NORTHWEST KANSAS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS
   SURROUNDING AREAS OF THE FRONT RANGE OF THE ROCKIES AND CENTRAL HIGH
   PLAINS...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   ACROSS PARTS OF THE MID ATLANTIC COAST REGION...

   ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON
   ACROSS PARTS OF SOUTHERN FLORIDA...

   ...SUMMARY...
   Thunderstorms may impact parts of the central high Plains late this
   afternoon and evening, accompanied by a risk for severe wind and
   hail.  Other strong storms are possible across the Mid Atlantic
   Coast region and parts of southern Florida.

   ...Synopsis...
   The elongated mid-level cold core, of large-scale upper troughing
   now encompassing most areas east of the Mississippi Valley, is in
   the process of pivoting northeastward across the southern Atlantic
   coast states.  As it continues northeastward, then northward, mostly
   off the Mid Atlantic coast through the remainder of the period, the
   mid Ohio Valley closed low appears likely to redevelop east
   northeastward into southern New England by 12Z Friday.  As it does,
   an associated occluded surface low should weaken across the
   mid/upper Ohio Valley, and the secondary surface low (now east
   southeast of the Washington D.C./Baltimore area) may eventually
   deepen near the southern New England coast.

   In the wake of the short wave impulse, mid-level heights are
   expected to rise, but models do suggest that mid/upper flow will
   remain at least broadly cyclonic across much of the south Atlantic
   Seaboard, including the Florida peninsula.  It also appears that a
   cold front, trailing from the Mid Atlantic surface low, may progress
   through the remainder of the central and southern Florida peninsula,
   before stalling and weakening.

   Upstream, broad mid/upper ridging is expected to continue developing
   northeastward across the southern Plains and middle/lower
   Mississippi Valley, to the south of broad upper troughing
   encompassing much of the northwestern U.S. into northern Plains.  At
   least a couple of significant perturbations are embedded within this
   latter feature, including one closed low which is forecast to
   gradually redevelop northeastward, across southern Saskatchewan and
   Manitoba.  Another closed low may form within a perturbation digging
   slowly southeastward through the northern intermountain region/Great
   Basin.  It does appear that a weaker impulse emerging from the Great
   Basin will progress east of the Colorado Rockies through much of the
   north central Plains by 12Z Friday.

   In response to the evolving pattern, a plume of seasonably high
   moisture content has already advected southeast and east of much of
   the northern Gulf of Mexico and Atlantic Seaboard (with the
   exception of south Florida).  However, modest moisture levels linger
   beneath the lower/mid tropospheric cyclone across the Ohio Valley
   and Mid Atlantic into portions of New England, ahead of a cold front
   across parts of the northern Plains into Great Basin, and within lee
   surface trough across the central/southern Plains.  And a plume of
   warm elevated mixed layer air is contributing to rather steep
   mid-level lapse rates as it advects across the central/southern
   Plains toward the mid/lower Mississippi Valley.

   ...Mid Atlantic region...
   The lack of stronger vertical shear and stronger, or at least more
   focused, mid-level forcing for ascent appear limiting factors
   concerning severe weather potential for today.  However, modest
   destabilization associated with insolation and cooling aloft may
   contribute to thermodynamic profiles supportive of scattered
   thunderstorm activity with at least some severe wind/hail potential
   (mostly marginal).

   ...South Florida...
   Model output suggests that a weak area of low pressure may develop 
   near/ahead of the cold front, in the vicinity or southeast of Lake
   Okeechobee, during the day today.  If this occurs, locally enhanced
   convergence may provide a focus for storm initiation, in the
   presence of sizable CAPE and lingering strong westerly mid/upper
   flow.  Otherwise, weak frontal/pre-frontal low-level convergence
   seems likely to limit the potential for sustained vigorous
   thunderstorm development.

   ...Central high Plains...
   A signal is evident, within the output of an ensemble of convection
   allowing model guidance, that suggests sustained organized storm
   development is at least possible within a corridor across parts of
   northeast Colorado into northwest Kansas late this afternoon and
   evening.  Thermodynamic profiles across this region probably will
   become favorable, with at least some further moistening beneath very
   steep mid-level lapse rates.  Given this environment, the deep layer
   shear probably will be sufficient to enhance any convective
   development.  However, deterministic model output appears at least a
   bit more unclear concerning supporting forcing for this activity. 
   As a result, severe weather potential seems largely conditional, but
   perhaps enough to maintain slight risk probabilities.

   ..Kerr/Cook.. 05/25/2017

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