Marine Weather and Tide Forecast for Bowleys Quarters, MD

NEAR TERM /THROUGH TONIGHT/
A multitude of hazards are in play today as a slow moving frontal system and accompanying trough intercept a moisture- rich air mass. While the 12Z IAD sounding recorded a precipitable water (PWAT) value of 2.17 inches, the 18Z RAP objective analysis suggests little change in the quality of moisture. With mainly 1.75 to 2.00 inch PWATs west of the Blue Ridge and 2.00 to 2.25 inch values to the east, tropospheric moisture levels generally reside close to the running daily maxima for mid-July. Not surprisingly, there is threat for some very heavy rainfall today with a Flood Watch (for flash flooding) currently spanning all counties east of the Alleghenies. This product remains in effect until midnight.

The atmosphere remains uncapped which has yielded a fairly active period of convection so far today. Activity has fired over the higher terrain as aided by a glancing blow from a shortwave passage to the north. At the same time, a north-south axis of showers and embedded thunderstorms continue along what appears to the bay breeze. This currently spans sections of Calvert County up into the Baltimore metro area.

Both national centers have outlook areas highlighted over the Mid-Atlantic region. The Weather Prediction Center has maintained a Moderate Risk for flash flooding that stretches from Fauquier County northeastward across the Washington, D.C.
and Baltimore metros up to the Mason-Dixon Line. At the same time, the Storm Prediction Center has upgraded to a Slight Risk for severe thunderstorms for locations along and east of I-81 (except far southern Maryland). Damaging wind gusts are the most likely hazard with such storms.

As a broad swath of scattered to numerous thunderstorms advance eastward from the Shenandoah Valley toward areas east of the Blue Ridge, an uptick in the severe storm threat is expected.
Owing to the nearly moist adiabatic-type profile in the column, overall lapse rates are rather subpar for severe convection.
However, some of the taller cores will be capable of producing water loaded downdrafts which can lead to damaging wind gusts.
All of this works its way eastward to the I-95 corridor in time for the evening rush hour. Given the expectation of some slower moving cells and numerous rounds of storms, some hefty rainfall rates and higher storm totals are possible. Up to 2 to 3 inches of rain are possible in an hour, with total amounts reaching the 4 to 6 inch range in an isolated spot or two.

All of this activity eventually reaches the Chesapeake Bay and far southern Maryland between 10 PM and midnight. After spending the day in the 80s to low 90s, mild temperatures continue into the overnight hours. Given no frontal passages ahead, ample tropical moisture remains in place. Thus, expect a mild/humid night ahead with low temperatures in the upper 60s to mid 70s (low/mid 60s for the mountains). Calm winds and saturated low- levels will enhance the potential for overnight patchy fog, some becoming locally dense in nature.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/
While a couple of days ago this frontal system was expected to cross through tonight, that will certainly not be happening. The current model guidance and forecast products support this boundary nearing the Mason-Dixon Line by Tuesday afternoon.
However, until all of today's convection clears the area tonight, it remains to be seen where this boundary truly settles. Unless this system completely clears the region, a seasonably warm and humid air mass should be in play for Tuesday. The larger difference between the two days is more limited upper forcing/support. Subtle height rises are expected along with less identifiable mesoscale perturbations.

While shower/thunderstorm chances are still in the 50 to 70 percent range, these should be more instability driven and be more pulse-like in nature. Cell motions may be on the slower side again, which coupled with previous days of heavy rainfall, will maintain a non-zero flash flood threat over the area. A Slight Risk for excessive rainfall has been maintained over pretty much all locations outside of Garrett and St. Mary's counties. Outside of another round of potentially active weather, Tuesday's highs are forecast to rise into the mid/upper 80s, with heat indices into the mid 90s. For the overnight, very little change is expected from previous nights with another round of patchy fog possible.

The boundary which lingers nearby into Wednesday is expected to lift northward as a warm front. A number of models show a slew of convective perturbations in the quasi-zonal flow. These should be an impetus to a more active convective day. However, given these are tied to storm-scale processes, there is plenty of uncertainty at this juncture. The chances for showers and thunderstorms rise to 60 to 80 percent. Forecast high temperatures push into the upper 80s to low 90s, which is accompanied by heat indices approaching the century mark. Being deeper into the tropical air mass, conditions will be milder overnight with lows in the low/mid 70s (closer to the upper 70s inside D.C. and Baltimore).

LONG TERM /THURSDAY THROUGH MONDAY/
A fairly persistent pattern is expected on the synoptic scale throughout the long term period. Flow aloft will generally be out of the west across northern portions of the CONUS/southern Canada through the period, with various weak disturbance embedded within zonal flow passing by to our north. We'll remain within a very warm and humid airmass through at least Friday. Thereafter, there's some uncertainty regarding whether or not we will get a true cold frontal passage that will drop temperatures and dewpoints.

Daily showers and thunderstorms are expected during the afternoon/evening hours as various disturbances pass off to our north. Temperatures will run near to slightly above normal with highs in the upper 80s to mid 90s, and lows in the upper 60s to mid 70s. Thunderstorms may be capable of producing isolated instances of flash flooding or damaging winds any of these days. The day that currently stands out the most from a synoptic standpoint will be Friday, when a cold front will approach the area from the north and west.

AVIATION /19Z MONDAY THROUGH SATURDAY/
Given a broad shield of semi-organized convection pushing eastward from the Shenandoah Valley, all terminals are expected to see multi-hour restrictions due to these thunderstorms.
Compared with the previous TAF packages, have narrowed down the time of most impact to around 20Z to 00Z, slightly earlier for the western terminals. Low visibility, gusty/erratic winds, and frequent lightning are the primary issues with any such storms.
The overall extent of wind gusts will be somewhat capped, but could still prove to be impactful with any stronger storm.

Showers and thunderstorms exit the area tonight with some patchy fog possible at nearly all TAF sites. IFR conditions are being forecast at KCHO. The following couple of days also present a risk of convection, particularly on Wednesday afternoon/evening.
It does appear the frontal system will not clear the region and actually retreat northward as a warm front on Wednesday. Until the region gets out of this pattern, daily convective chances will support a potential for afternoon/evening restrictions.

Prevailing VFR conditions are expected on both Thursday and Friday. Winds will be out of the southwest on Thursday, and then west on Friday.

MARINE
Gradients largely remain on the weaker side with gusts generally averaging around 10 knots or less. However, convective chances are elevated today with the area at risk of flash flooding and severe thunderstorms. For this evening and early overnight hours, a few Special Marine Warnings may be required for the stronger storms.

Tuesday and Wednesday also carry a risk of convection, with the latter likely being the more active of the two days. Thus, hazardous boating conditions are possible at times, particularly during the afternoon/evening periods. As a warm front lifts northward on Wednesday, an uptick in southerly winds are expected, particularly for the evening to overnight hours.
Small Craft Advisories may be needed for the southern most waters as gusts push to near 20 knots.

Sub-SCA level winds are expected over the waters on both Thursday and Friday. Winds will generally be out of the southwest on Thursday and west on Friday. SMWs may potentially be needed as a result of thunderstorms either afternoon or evening.



HYDROLOGY
A Flood Watch for the threat of flash flooding is in effect until midnight across all locations east of the Allegheny Front. A tropical air mass remains in place across the area.
With precipitable water values into the 2 to 2.25 inch range, this easily rises into the 95th percentile for mid-July. Very high rainfall rates are possible, generally up to 2 to 3 inches per hour within some of the more potent and slow moving cores.
Areas hit more recently by flooding rains will certainly be more vulnerable to additional heavy thunderstorms today. While most will not see this, storm totals approaching 4 to 6 inches are not out of the question in areas of training/slow moving convection.

TIDES/COASTAL FLOODING
A prolonged period of southeasterly winds will lead to elevated tidal anomalies through midweek. This carries most of the tidal locations into Action stage, particularly during the higher of the two astronomical high tide cycles. Sensitive locations, such as Annapolis, are forecast to stay just below Minor stage during the high tide cycles this morning.

LWX WATCHES/WARNINGS/ADVISORIES
DC...Flood Watch until midnight EDT tonight for DCZ001.
MD...Flood Watch until midnight EDT tonight for MDZ003>006-008-011- 013-014-016>018-501>508.
VA...Flood Watch until midnight EDT tonight for VAZ025>031-036>040- 050-051-053>057-501-502-505>508-526-527.
WV...Flood Watch until midnight EDT tonight for WVZ050>053-055-503- 504.
MARINE...Flood Watch until midnight EDT tonight for ANZ530.